PCB 3036 GENTICS EXAM #1 2019

PCB 3036 GENTICS EXAM #1 2019 Chapter 1 1. The case of albinism among the Hopi Indians of Black Mesa is different from other cases of albinism because of all of the following EXCEPT: a. the albinism did not involve vision defects. 2. Genetics has played a key role in which of the following areas? a. Agriculture, medicine, pharmaceutical production 3. Genetic variation in populations: a. provides the basis of adaptation. 4. Genetics as a discipline can be subdivided into all of the following EXCEPT: a. acquisition genetics. 5. Early notions of heredity that do not seem to describe it accurately include all of the following EXCEPT: a. germ-plasm theory. 6. While modern genetics starts with the experiments of Gregor Mendel in 1866, it wasn't until the start of the 20th century that those studies became well known, amplifying the work of: a. Sutton, who proposed that genes were on chromosomes., Morgan, who identified fruit fly mutations., Haldane and others who used populations to connect genetics to evolution. 7. Prokaryotes and eukaryotes differ in that: a. None of the above. 8. Genes: a. are carried on chromosomes., come in pairs in eukaryotic cells., come in alternative forms, known as alleles. 9. Phenotypes are: a. measurable traits of an organism., not inherited directly. 10. The sexual life cycle involves: a. mitosis, followed by meiosis and fertilization. 11. The flow of information is as follows: a. DNA to RNA to protein. 12. Mutations are changes of DNA: a. that can affect a single gene., that can affect large regions of chromosomes., that can be passed on to daughter cells. 13. Which theory shares some conceptual overlap with pangenesis? a. Germ-plasm 14. Domestication of plants and animals first began about a. 10,000–12,000 years ago. 15. Which of the following is a correct statement? A. The major difference between eukaryotic and prokaryotic cells is the presence or absence of a defined nucleus, respectively 16. Heritable changes in genetic information would affect a. DNA, RNA, and Protein 17. Which of the following examples of scientists and subfields of genetics are matched incorrectly? a. Morgan—molecular genetics 18. Which of the following would likely make the best model genetic organism for studying developmental mechanisms of eukaryotic gene regulation? a. Fruit fly 19. Which topic would be covered within the subdiscipline of molecular genetics? a. Determining the type of change in DNA that produced a mutation responsible for a genetic disease 20. The first evidence that humans understood and applied principles of heredity is found in a. early domestication of plants and animals 21. Which topic would be covered within the subdiscipline of population genetics? a. Effect of small numbers of individuals on changes in the frequencies of an allele 22. What is the relationship between genes and alleles? a. Alleles refer to the versions of a gene. 23. Which of the following statements describes the germ-plasm theory? a. Cells in the reproductive organs contain a complete set of genetic information that is transferred directly to the gametes. 24. What is the relation between genetics and evolution? a. Evolution involves change in the frequency of genetic variants. 25. The idea that particles carry genetic information from different parts of the body to the reproductive organs is known as . a. pangenesis 26. Which topic would be covered within the subdiscipline of molecular genetics? a. Determining the type of change in DNA that produced a mutation responsible for a genetic disease 27. Which theory of inheritance suggested that all traits are inherited from one parent? a. Preformationism 28. Which theory has contributed the most to disprove the concept of blending inheritance? a. Mendelian inheritance 29. Which of the following statements about Hopi culture MOST directly explains the high frequency of albinism observed among members of this tribe? a. Albino males did not work the fields and spent more time with the women of the tribe, which allowed them to have more children. 30. Genetics is important to all of us because a. All of the above choices are ways in which genetics is important to us. 31. Which of the following is NOT an example of the role of genetics in society today a. Production of crude oil for manufacturing processes and gasoline synthesis 32. Genetics is crucial to modern biology because a. the study of genetics supports many other biological disciplines. 33. Exploration of the chemical nature of the gene, including the structure, organization, and function of genes at a molecular level summarizes genetics. a. Molecular 34. Which of the following characteristics of model genetic organisms does NOT make an organism useful for genetic studies? a. Small, manageable numbers of progeny 35. When and where did agriculture first arise? a. 10,000 to 12,000 years ago in the Middle East 36. What role did genetics play in the development of the first domesticated plants and animals? a. Farmers selectively bred individual wild plants and animals that had useful characteristics with others that had similar useful traits. 37. How does the notion of pangenesis differ from the germ-plasm theory? a. Pangenesis proposes that gemmules carry information from various parts of the body to the reproductive organs, where they are passed to the gametes and then to the embryo at the moment of conception; the germ-plasm theory proposes that reproductive cells contain the genetic information required to make a complete organism. 38. How is the concept of the inheritance of acquired characteristics related to the notion of pangenesis? a. The concept of traits acquired within a lifetime passed down from the parents to offspring is supported by the notion of pangenesis where genetic information traveling from different parts of the body ends up in reproductive organs. 39. According to preformationism, a. the offspring result from a miniature adult that is already preformed in the sperm or egg. 40. A major component of the theory of blending inheritance that differs from the concept of preformationism is that a. the egg and sperm from the parents contain material that blends upon conception, influencing the development of the offspring. 41. How did developments in botany in the seventeenth and eighteenth centuries contribute to the rise of modern genetics? a. Botanists of the seventeenth and eighteenth centuries developed new techniques for creating plant hybrids, providing essential background work for Mendel. 42. Which of the following advances in genetics was NOT made in the twentieth century? a. Demonstration that the nucleus had a role in fertilization 43. What are the two basic types of cells from a structural perspective? a. Prokaryotic cells and eukaryotic cells 44. How do prokaryotic and eukaryotic cells differ? a. Prokaryotic cells do not have a nucleus, whereas eukaryotic cells do have a nucleus. 45. The relations between genes, DNA, and chromosomes are BEST summarized by which statement? a. Genes are composed of DNA nucleotide sequences that are located at specific positions on chromosomes 46. What is the relation between genetics and evolution? a. Genetic variation is the foundation of evolutionary change. And Evolution is the change in genetic composition of a population over time. 47. Of the following genetic topics, which one focuses on transmission genetics? a. Analysis of pedigrees to determine the probability of someone inheriting a trait and Study of how the inheritance of traits encoded by genes on sex chromosomes (sex-linked traits) differs from the inheritance of traits encoded by genes on autosomal chromosomes (autosomal traits) 48. Of the following genetic topics, which one focuses on molecular genetics? a. Examination of the nucleotide sequences found at the ends of chromosomes and Mechanisms that ensure a high degree of accuracy in DNA replication 49. Of the following genetic topics, which one focuses on population genetics? a. Study of people on a small island to determine why a genetic form of asthma is prevalent on the island and Effect of nonrandom mating on the distribution of genotypes among a group of animals 50. Genetics is said to be both a very old science and a very young science. This statement means that a. although humans have applied heredity principles for thousands of years, understanding of the underlying genetic principles developed rapidly only during the last (twentieth) century. 51. Which description CORRECTLY describes the theory of preformationism? a. All traits are inherited from one parent. 52. Which description CORRECTLY describes the theory of pangenesis? a. Cells of different tissues contain different genetic information, which is carried to the reproductive organs to be passed to the gametes. 53. Which description CORRECTLY describes the germ-plasm theory? a. Each reproductive cell contains a complete set of genetic information. 54. Pangenesis and the germ-plasm theory are similar in that both claim that a. the passage of genetic information occurs through the reproductive organs. 55. Preformationism differs from blending inheritance in that a. the concept of preformationsim postulates that the offspring result from a miniature adult form (the homunculus) that is already preformed in the sperm or egg. And the concept of preformationsim postulates that all traits would be inherited from one parent 56. The concept of inheritance of acquired characteristics differs from our modern theory of heredity in that the concept of a. inheritance of acquired characteristics postulates that traits acquired within a lifetime can be transmitted from the parents to offspring. 57. A difference between eukaryotic cells and prokaryotic cells is that a. eukaryotic cells have a nucleus containing chromosomal DNA. 58. What is the relation between genes and alleles? a. Alleles are alternative forms of a gene. 59. Which of the following statements BEST represents the relation between genotype and phenotype? a. The expression of genes of a particular genotype, through interactions with environmental factors, produces the phenotype. 60. Which of the following statements helps to distinguish DNA and RNA? a. DNA contains thymine but RNA does not. 61. What is the relation between DNA and chromosomes? a. Chromosomes are composed of DNA and associated proteins. 62. The type of albinism that arises with high frequency among Hopi Native Americans (discussed in the introduction to this chapter) is most likely oculocutaneous albinism type 2, due to a defect in the OCA2 gene on chromosome 15. After you do some research on the Internet, choose the explanation that BEST explains how the phenotype for this type of albinism differs from phenotypes for other forms of albinism in humans a. OCA type 2–affected individuals may have creamy white skin and hair color that ranges from light brown to light yellow. And The symptoms are less severe in tyrosinase-positive oculocutaneous albinism type 2 individuals than in tyrosinase- deficient individuals. 63. Suppose that life exists elsewhere in the universe. All life must contain some type of genetic information, but alien genomes might not consist of nucleic acids and have the same features as those found in the genomes of life on Earth. What might be the common features of all genomes, no matter where they exist? a. An ability to store the entire set of information an organism needs to carry for reproduction and development Chapter 2 1. Gregor Mendel used peas in his experiments for all of the following reasons EXCEPT: a. he could grow the plants all year in Moravia 2. A heterozygote is an individual: a. with two different alleles of a gene. 3. In a monohybrid cross: a. only a single character is studied. And parents differ from each other in only one trait 4. Mendel's first law is described by all of the following EXCEPT: a. it is known as the law of independent assortment. 5. The events of meiosis explain Mendel's law of segregation in that: a. meiosis is a reductional division. And meiosis produces cells that are haploid. And fertilization produces a new diploid cell from two haploid gametes. 6. Punnett squares are NOT: a. filled in to represent meiosis. 7. According to the multiplication rule of probability, the chance of crossing two pea plants that are heterozygous for height and have none of four offspring showing the recessive short phenotype is: a. ¾ × ¾ × ¾ × ¾. 8. The test cross: a. gives results either 100% dominant or 1:1 dominant: recessive 9. The dihybrid cross: a. is a cross that involves two traits. 10. The law of independent assortment describes the behavior of traits: a. only if genes are on different chromosomes. 11. Mendel's law of independent assortment depends on the events of meiosis because: a. different chromosomes will segregate independently during anaphase I. 12. If we apply a branch diagram to a dihybrid cross between organisms heterozygous for both genes, we can calculate: a. the chance of an individual being recessive for both is 1/16 13. Mendel observed that the number of peas that had an expected phenotype was rarely exactly what was predicted based on his laws. This can be explained by: a. random use of pollen without regard to its genotype. 14. In applying a chi-square test, the square of the deviation is divided by the expected results. This means that: a. larger sample sizes will produce more accurate results. 15. The probability of rolling a single die and obtaining a 2 is 1/6. The probability of rolling a single die and obtaining a 5 is 1/6. What is the probability of rolling a single die and obtaining either a 2 or a 5? a. 1/3 16. How could two genetically identical oak trees have different heights when tree height is a heritable trait? a. The height of the trees may differ if one of them received more sunlight, water, and fertilizer than the other. 16. Which of the following characteristics of an organism would make it the most difficult for studying heredity? a. Large size, making them expensive to maintain 17. The probability of rolling a single die and obtaining a 2 is 1/6. What is the probability of rolling two dice and obtaining a 2 on one and a 5 on the other? a. 1/36 18. Which parents produce a 3:1 phenotypic ratio in a simple genetic cross with dominance? a. Aa x Aa 19. A chi-square test is calculated for the observed and expected numbers of progeny from a genetic cross. The probability associated with the chi-square value is 0.023. This is the probability that a. the difference between observed and expected numbers is due to chance. 20. The genetic principle that states that alleles at one locus do not affect the segregation of alleles at another locus is called the a. principle of independent assortment 21. What would be the phenotypic ratio produced by a cross between AaBband aabb? a. 1:1:1:1 22. When does the principle of independent assortment (Mendel's second law) occur in mitosis and/or meiosis? a. Anaphase I of meiosis 23. A dibybrid cross is performed and sixteen offspring are counted. Four phenotypes are expected for this cross. Interestingly, only three of the phenotypic classes are found among the offspring. If a chi-square value for this cross is calculated to be 1.1, what is the probability that the difference between the observed and expected numbers of offspring is due to chance? a. Between 0.9 and 0.5 24. Predict which of the following hypothetical organisms would be the most useful for studying heredity. a. An insect that reaches sexual maturity in 9 days and can lay 1000 eggs per week 25. What would be the probability of obtaining the phenotype AB from a crossAABB x aabb? a. 1 26. The principle of independent assortment is an extension of the principle of a. segregation 27. What would be the probability of obtaining the phenotype Ab from a crossAabb x aabb? a. 1/2 28. A 9:3:3:1 phenotypic ratio is produced by which cross? a. AaBb x AaBb 29. Mendel's approach to the study of heredity was effective because a. he adopted an experimental approach. And he conducted studies on an appropriate model organism. And he kept careful records. 30. Where in mitosis and/or meiosis does the principle of segregation (Mendel's first law) occur? a. Anaphase I of meiosis 31. A monohybrid cross between plants heterozygous for tall and short alleles is expected to produce two phenotypic classes of offspring. How many degrees of freedom can we use in the chi-square test for this cross? a. 1 32. A monohybrid cross is performed and many offspring of two expected phenotypes are observed. However, the observed numbers of offspring are different than the expected numbers of offspring. If a chi-square value for this cross is calculated to be 0.05, what is the probability that the difference between the observed and expected numbers of offspring is due to chance? a. Greater than 0.5 33. Crossing an individual of unknown genotype to an individual with a homozygous recessive genotype is known as a a. testcross 34. Red (A) is dominant to white (a). Two red individuals are crossed and some white progeny are produced. What are the most likely genotypes of the two red parents of this cross? a. Aa x Aa 35. A 1:2:1 genotypic ratio in the progeny is produced by which cross? a. Aa x Aa 36. Which genetic principle states that each individual possesses two alleles coding for a trait and that these alleles separate when gametes are formed? a. Principle of segregation 37. A can be used to predict the results of a genetic cross. a. Punnett square 38. Why did Gregor Mendel end his genetics experiments? a. Mendel became too busy after he was elected abbot of his monastery. 39. A is the set of alleles possessed by an individual organism. a. genotype 40. Gregor Mendel received broad scientific training during his early university studies. Which of the following subjects do you think provided Mendel with the necessary knowledge to analyze phenotypic ratios from his experiments? a. Mathematics 41. A 1:1 genotypic ratio in the progeny is usually produced by which cross? a. Aa x aa - Why was Mendel's approach to the study of heredity so successful? - He chose to work with a plant that was easy to cultivate, grew relatively rapidly, and produced many offspring whose phenotype was easy to determine., By looking at each trait separately and counting the numbers of the different phenotypes, he was able to detect mathematical ratios of progeny phenotypes., He adopted an experimental approach and applied the scientific method. From his observations, he proposed hypotheses that he was then able to test empirically., The seven characteristics he chose to study were important because they exhibited only a few distinct phenotypes and did not show a range of variation. - What is the difference between genotype and phenotype? - Phenotype refers to the physical manifestation of a trait, whereas genotype refers to the genes or sets of alleles found within an individual. - What is the principle of segregation? Why is it important? - The principle of segregation states that a diploid organism possesses two alleles for any one particular trait and that these alleles separate during the formation of gametes. It explains how the genotypic ratios in the haploid gametes are produced. - How are Mendel's principles different from the concept of blending inheritance discussed in Chapter 1? - According to the concept of blending inheritance, offspring result from a blending of their parents' genetic material, According to the concept of blending inheritance, once blended, the genetic material from each parent is no longer discrete units that remain separated within an individual organism, According to Mendel's principles, alleles (or genetic factors) are discrete units that remain separated within an individual organism., According to the concept of blending inheritance, genetic material once blended cannot be separated in future generations. - What is the concept of dominance? - The concept of dominance states that when two different alleles are present in a genotype, only the dominant allele is observed in the phenotype. - The multiplication rule of probability - indicates that the probability of two events occurring together is the product of their probabilities of occurring independently. And allows for predicting the probability of two or more independent events occurring together - The additive rule of probability - allows for predicting the probability of a single event that can occur in two or more ways. And indicates that the probability of a single mutually exclusive event can be determined by adding the probabilities of the two or more different ways in which this single event could take place. - Which of the following crosses would likely produce a genotypic ratio of 1:2:1? - Aa × Aa - Which of the following crosses would likely produce a genotypic ratio of 1:1? - Aa × aa - The chromosome theory of heredity states that - genes are located on chromosomes. - Why was the chromosome theory of heredity important? - It explained the biological basis for Mendel's principles of heredity - According to the principle of independent assortment - alleles at different loci separate independently of each other. - In which phase of meiosis are the principles of segregation and independent assortment at work? - Anaphase I - In which phase of mitosis are the principles of segregation and independent assortment at work? - These principles do not apply to mitosis. - How is the chi-square goodness-of-fit test used to analyze genetic crosses? - To evaluate the role of chance in causing deviations between observed and the expected numbers of offspring produced in a genetic cross - What does the probability associated with a chi-square value indicate about the results of a cross? - It indicates the likelihood that random chance produced the deviations of the observed numbers from the expected numbers - The inheritance of red hair was discussed in the introduction to this chapter. At times in the past, red hair in humans was thought to be a recessive trait and, at other times it was thought to be a dominant trait. What features of heritance would red hair be expected to exhibit as a recessive trait? - In matings between two red hair parents, all of the offspring would be expected to have red hair - The inheritance of red hair was discussed in the introduction to this chapter. At times in the past, red hair in humans was thought to be a recessive trait and at other times, it was thought to be a dominant trait. What features of heritance would red hair be expected to exhibit as a dominant trait? - Red hair would appear only in children who had at least one parent with red hair - Which of the following is a characteristic of an organism that would make it suitable for studies of the principles of inheritance? - Grows rapidly, producing many generations in a short period of time, Produces large numbers of offspring, Easy to grow and maintain, Has distinctive phenotypes that are easy to recognize - Which of the following organisms does NOT have the characteristics that would make it suitable for studies of the principles of inheritance? - Loxodonta africana, an elephant - In cucumbers, orange fruit color (R) is dominant over cream fruit color (r). A cucumber plant homozygous for orange fruit is crossed with a plant homozygous for cream fruit. The F1 are intercrossed to produce the F2. What are genotypes of the parents, the F1, and the F2? - Parents (RR× rr); F1 (Rr); F2 (RR, Rr, and rr) - In cucumbers, orange fruit color (R) is dominant over cream fruit color (r). A cucumber plant homozygous for orange fruit is crossed with a plant homozygous for cream fruit. Give the genotypes and phenotypes of the offspring of a backcross between the F1 and the orange parent - Orange (RR), Orange (Rr) - In cucumbers, orange fruit color (R) is dominant over cream fruit color (r). A cucumber plant homozygous for orange fruit is crossed with a plant homozygous for cream fruit. Give the genotypes and phenotypes of a backcross between the F1 and the cream parent - Orange (Rr), Cream (rr) - (below) shows three girls, one of whom has albinism. Could the three girls shown in the photograph be sisters? Why or why not? - Yes, the girls could be sisters. Albinism is inherited as an autosomal recessive trait, so the children could be sisters if the parents were heterozygous. - What is the BEST explanation for the inheritance of the tan and red seeds in this plant? - It is likely a monohybrid cross with the tan seed allele dominant to the red seed allele - White (w) coat color in guinea pigs is recessive to black (W). In 1909, W. E. Castle and J. C. Phillips transplanted an ovary from a black guinea pig into a white female whose ovaries had been removed. They then mated this white female with a white male. All the offspring from the mating were black in color (W. E. Castle and J. C. Phillips, 1909, Science 30:312–313). Which of the following statements BEST explains the results of this cross? - The color of the offspring was determined by genes in the transplanted ovary, not the genes of the female who gave birth. - White (w) coat color in guinea pigs is recessive to black (W). In 1909, W. E. Castle and J. C. Phillips transplanted an ovary from a black guinea pig into a white female whose ovaries had been removed. They then mated this white female with a white male. All the offspring from the mating were black in color (W. E. Castle and J. C. Phillips. 1909, Science 30:312–313). Give the genotype of the offspring from this cross -Ww - White (w) coat color in guinea pigs is recessive to black (W). In 1909, W. E. Castle and J. C. Phillips transplanted an ovary from a black guinea pig into a white female whose ovaries had been removed. They then mated this white female with a white male. All the offspring from the mating were black in color (W. E. Castle and J. C. Phillips, 1909, Science 30:312–313). What, if anything, does this experiment indicate about the validity of the pangenesis and the germ-plasm theories discussed in Chapter 1? - Both answers A and B describe outcomes that indicate the validity of the germ-plasm theory but not the pangenesis theory. - In cats, blood type A results from an allele I(A) that is dominant over an allele i(B) that produces blood type B. There is no O blood type. The blood types of male and female cats that were mated and the blood types of their kittens follow. Give the MOST likely genotypes for the parents of the litter - Male I(A)i(B) × Female i(B)i(B) - In cats, blood type A results from an allele I(A) that is dominant over an allele i(B) that produces blood type B. There is no O blood type. The blood types of male and female cats that were mated and the blood types of their kittens follow. Give the MOST likely genotypes for the parents of the litter - Male i(B)i(B) × Female i(B)i(B) - In cats, blood type A results from an allele I(A) that is dominant over an allele i(B) that produces blood type B. There is no O blood type. The blood types of male and female cats that were mated and the blood types of their kittens follow. Give the MOST likely genotypes for the parents of the litter. - Male i(B)i(B) × Female I(A)I(A) - In cats, blood type A results from an allele I(A) that is dominant over an allele i(B) that produces blood type B. There is no O blood type. The blood types of male and female cats that were mated and the blood types of their kittens follow. Give the MOST likely genotypes for the parents of the litter. - Male I(A)i(B) × Female I(A)i(B) - (Problem 18) In cats, blood type A results from an allele I(A) that is dominant over an allele i(B) that produces blood type B. There is no O blood type. The blood types of male and female cats that were mated and the blood types of their kittens follow. Give the MOST likely genotypes for the parents of the litter. - All of the above are possible genotypes for the parents - In cats, blood type A results from an allele I(A) that is dominant over an allele i(B) that produces blood type B. There is no O blood type. The blood types of male and female cats that were mated and the blood types of their kittens follow. Give the MOST likely genotypes for the parents of the litter. - Male I(A)i(B) × Female i(B)i(B) - shows the results of a cross between a tall pea plant and a short pea plant. What phenotypes and proportions will be produced if a tall F1 progeny is backcrossed to the short parent? - 1/2 tall and 1/2 short - shows the results of a cross between a tall pea plant and a short pea plant. What phenotypes and proportions will be produced if a tall F1 progeny is backcrossed to the tall parent? - 3/4 tall and 1/4 short - Joe has a white cat named Sam. When Joe crosses Sam with a black cat, he obtains 1/2 white kittens and 1/2 black kittens. When the black kittens are interbred, they produce all black kittens. On the basis of these results, would you conclude that white or black coat color in cats is a recessive trait and why? - Black is the recessive trait because the black kitten offspring only produced black offspring when interbred, suggesting they are all homozygous for black coat color - In sheep, lustrous fleece results from an allele (L) that is dominant over an allele (l) for normal fleece. A ewe (adult female) with lustrous fleece is mated with a ram (adult male) with normal fleece. The ewe then gives birth to a single lamb with normal fleece. What are the likely genotypes of the two parents? - ewe (Ll); ram (ll) - Alkaptonuria is a metabolic disorder in which affected persons produce black urine. Alkaptonuria results from an allele (a) that is recessive to the allele for normal metabolism (A). Sally has normal metabolism, but her brother has alkaptonuria. Sally's father has alkaptonuria, and her mother has normal metabolism. What is Sally's genotype? - Aa - In humans, alkaptonuria is a metabolic disorder in which affected persons produce black urine. Alkaptonuria results from an allele (a) that is recessive to the allele for normal metabolism (A). Sally has normal metabolism, but her brother has alkaptonuria. Sally's father has alkaptonuria, and her mother has normal metabolism. What is the genotype of Sally's brother and Sally's father? - aa - In humans, alkaptonuria is a metabolic disorder in which affected persons produce black urine. Alkaptonuria results from an allele (a) that is recessive to the allele for normal metabolism (A). Sally has normal metabolism, but her brother has alkaptonuria. Sally's father has alkaptonuria, and her mother has normal metabolism. If Sally's parents have another child, what is the probability that this child will have alkaptonuria? - 50% - In humans, alkaptonuria is a metabolic disorder in which affected persons produce black urine. Alkaptonuria results from an allele (a) that is recessive to the allele for normal metabolism (A). Sally has normal metabolism, but her brother has alkaptonuria. Sally's father has alkaptonuria, and her mother has normal metabolism. If Sally marries a man with alkaptonuria, what is the probability that their first child will have alkaptonuria? - 50% - Suppose that you are raising Mongolian gerbils. You notice that some of your gerbils have white spots, whereas others have solid coats. What type of cross could you carry out to determine whether white spots are due to a recessive allele? - Cross a gerbil with white spots to another gerbil with a solid coat. If this cross produces either all solid or one-half gerbils with solid coats and one-half with white spots, then white spots are due to a recessive allele. - Hairlessness in American rat terriers is recessive to the presence of hair. Suppose that you have a rat terrier with hair. How can you determine whether this dog is homozygous or heterozygous for the hairy trait? - Cross your rat terrier with a hairless rat terrier - What is the probability of rolling one six-sided die and obtaining a 2? - 1/6 - What is the probability of rolling one six-sided die and obtaining a 1 or a 2? - 1/3 - What is the probability of rolling one six-sided die and obtaining an even number? - ½ - What is the probability of rolling one six-sided die and obtaining any number but a 6? - 5/6 - What is the probability of rolling two six-sided dice and obtaining a 2 and a 3? - 1/18 - What is the probability of rolling two six-sided dice and obtaining a 6 and a 6? - 1/36 - What is the probability of rolling two six-sided dice and obtaining at least one 6 - 11/36 - What is the probability of rolling two six-sided dice and obtaining an even number on both dice - ¼ - What is the probability of rolling two six-sided dice and obtaining an even number on at least one die - ¾ - In a family of seven children, what is the probability of obtaining all boys - 1/128 - In a family of seven children, what is the probability of obtaining all children of the same sex - 1/64 - In a family of seven children, what is the probability of obtaining six girls and one boy - 7/128 - In a family of seven children, what is the probability of obtaining four boys and three girls - 35/128 - in a family of seven children, what is the probability of obtaining four girls and three boys - 35/128 - Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that a sperm from the father will contain the PKU allele? - ½ - Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that an egg from the mother will contain the PKU allele - ½ - Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that their next child will have PKU - ¼ - Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that their next child will be heterozygous for the PKU gene - ½ - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the black fur allele (B) will be present in each cell from an F1 black guinea pig at G1 - 1 in each cell - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the black fur allele (B) will be present in each cell from an F1 black guinea pig at G2? - 2 in each cell - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the black fur allele (B) will be present in each cell from an F1 black guinea pig at metaphase of mitosis? - 2 in each cell - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the black fur allele (B) will be present in each cell from an F1 black guinea pig at metaphase I of meiosis? Assume that no crossing over take place. - 2 in each cell - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the black fur allele (B) will be present in each cell from an F1 black guinea pig at metaphase II of meiosis? Assume that no crossing over takes place. - 2 but only in one-half of the cells; the remaining one-half will not contain the B allele. - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the black fur allele (B) will be present in each cell from an F1 black guinea pig after cytokinesis following meiosis? Assume that no crossing over takes place - 1 but only in one-half of the cells; the remaining one-half will not contain the B allele - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the brown fur allele (b) will be present in each cell from an F1 brown guinea pig at G1? - 2 in each cell - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the brown fur allele (b) will be present in each cell from an F1 brown guinea pig at G2? - 4 in each cell - in guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the brown fur allele (b) will be present in each cell from an F1 brown guinea pig at metaphase of mitosis? - 4 in each cell - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the brown fur allele (b) will be present in each cell from an F1 brown guinea pig at metaphase I of meiosis? Assume that no crossing over takes place. - 4 in each cell - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the brown fur allele (b) will be present in each cell from an F1 brown guinea pig at metaphase II of meiosis? Assume that no crossing over takes place. - 2 in each cell - In guinea pigs, the allele for black fur (B) is dominant over the allele for brown (b) fur. A black guinea pig is crossed with a brown guinea pig, producing five F1 black guinea pigs and six F1 brown guinea pigs. How many copies of the brown fur allele (b) will be present in each cell from an F1 brown guinea pig after cytokinesis following meiosis? Assume that no crossing over takes place - 1 in each cell - In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2. What will be the phenotypic ratio in the F2? - 9/16 bitter fruit, yellow spots; 3/16 bitter fruit, no spots; 3/16 sweet fruit, yellow spots, and 1/16 sweet fruit, no spots - In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. If an F1 plant is backcrossed with the bitter, yellow-spotted parent, what phenotypes and proportions are expected in the offspring? - All bitter fruit with yellow spots - In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and proportions are expected in the offspring? - 1/4 bitter fruit, yellow spots; 1/4 bitter fruit, no spots; 1/4 sweet fruit, yellow spots; and 1/4 sweet fruit, no spots - shows the results of a dihybrid cross involving seed shape and seed color. What proportion of the round and yellow F2 progeny from this cross is homozygous at both loci? - 1/9 - shows the results of a dihybrid cross involving seed shape and seed color. What proportion of the round and yellow F2 progeny from this cross is homozygous at least at one locus? - 5/9 - In cats, curled ears result from an allele (Cu) that is dominant over an allele (cu) for normal ears. Black color results from an independently assorting allele (G) that is dominant over an allele for gray (g). A gray cat homozygous for curled ears is mated with a homozygous black cat with normal ears. All the F1 cats are black and have curled ears. If two of the F1 cats mate, what phenotypes and proportions are expected in the F2? - 9/16 black cats, curled ears; 3/16 black cats, normal ears; 3/16 gray cats, curled ears; and 1/16 gray cats, normal ears - In cats, curled ears result from an allele (Cu) that is dominant over an allele (cu) for normal ears. Black color results from an independently assorting allele (G) that is dominant over an allele for gray (g). A gray cat homozygous for curled ears is mated with a homozygous black cat with normal ears. All the F1 cats are black and have curled ears. An F1 cat mates with a stray cat that is gray and possesses normal ears. What phenotypes and proportions of progeny are expected from this cross? - 1/4 black cats, curled ears; 1/4 black cats, normal ears; 1/4 gray cats, curled ears and 1/4 gray cats, normal ears - The following two genotypes are crossed: AaBbCcddEe × AabbCcDdEe. What will be the proportion of the genotype AaBbCcDdEe among the progeny of this cross? - 1/32 - The following two genotypes are crossed: AaBbCcddEe × AabbCcDdEe. What will be the proportion of the genotype AabbCcddee among the progeny of this cross? -1/64 - The following two genotypes are crossed: AaBbCcddEe × AabbCcDdEe. What will be the proportion of the genotype aabbccddee among the progeny of this cross? - 1/256 - The following two genotypes are crossed: AaBbCcddEe × AabbCcDdEe. What will be the proportion of the genotype AABBCCDDEE among the progeny of this cross? - It will not occur. - In mice, an allele for apricot eyes (a) is recessive to an allele for brown eyes (a+). At an independently assorting locus, an allele for tan (t) coat color is recessive to an allele for black (t+) coat color. A mouse that is homozygous for brown eyes and black coat color is crossed with a mouse having apricot eyes and a tan coat. The resulting F1 are intercrossed to produce the F2. In a litter of eight F2 mice, what is the likelihood that two will have apricot eyes and tan coats? - 7.4% - In cucumbers, dull fruit (D) is dominant over glossy fruit (d), orange fruit (R) is dominant over cream fruit (r), and bitter cotyledons (B) are dominant over nonbitter cotyledons (b). The three characters are encoded by genes located on different pairs of chromosomes. A plant homozygous for dull, orange fruit and bitter cotyledons is crossed with a plant that has glossy, cream fruit and nonbitter cotyledons. The F1 are intercrossed to produce the F2. Give the expected proportions of offspring with a dull, orange, and bitter phenotype in the F2. - 27/64 - In cucumbers, dull fruit (D) is dominant over glossy fruit (d), orange fruit (R) is dominant over cream fruit (r), and bitter cotyledons (B) are dominant over nonbitter cotyledons (b). The three characters are encoded by genes located on different pairs of chromosomes. A plant homozygous for dull, orange fruit and bitter cotyledons is crossed with a plant that has glossy, cream fruit and nonbitter cotyledons. The F1 are intercrossed to produce the F2. Give the expected proportions of offspring with a glossy, cream, nonbitter phenotype in the F2. - 1/64 - In cucumbers, dull fruit (D) is dominant over glossy fruit (d), orange fruit (R) is dominant over cream fruit (r), and bitter cotyledons (B) are dominant over nonbitter cotyledons (b). The three characters are encoded by genes located on different pairs of chromosomes. A plant homozygous for dull, orange fruit and bitter cotyledons is crossed with a plant that has glossy, cream fruit and nonbitter cotyledons. The F1 are intercrossed to produce the F2. Give the expected proportion of offspring with a dull, orange, and bitter phenotype or a glossy, orange, and bitter phenotype in the F2. - 9/16 - In cucumbers, dull fruit (D) is dominant over glossy fruit (d), orange fruit (R) is dominant over cream fruit (r), and bitter cotyledons (B) are dominant over nonbitter cotyledons (b). The three characters are encoded by genes located on different pairs of chromosomes. A plant homozygous for dull, orange fruit and bitter cotyledons is crossed with a plant that has glossy, cream fruit and nonbitter cotyledons. An F1 plant is crossed with a plant that has glossy, cream fruit and nonbitter cotyledons. Give the expected proportions among the progeny of this cross with a glossy, cream, bitter phenotype. - 1/8 - On the basis of these results, what is the MOST likely mode of inheritance of the burnsi phenotype? - The spotting likely is a monohybrid trait with the burnsi allele dominant to the pipiens allele in leopard frogs - Give the MOST likely genotypes of the parent in each cross using - burnsi (Pp) × burnsi (Pp); burnsi (Pp) × pipiens (pp); burnsi (Pp) × pipiens (pp) - Use a chi-square test to evaluate the fit of the observed numbers of progeny to the number expected from the cross burnsi × burnsi that produced 39 burnsi, 6 pipiens. Assume that the burnsi allele is dominant to the pipiens allele and that the burnsi parents are heterozygous. - With one degree of freedom, the chi-square value is less than 3.841 for a probability value of greater than 0.1, so the deviation between observed and expected was likely to occur by chance. - Use a chi-square test to evaluate the fit of the observed numbers of progeny to the number expected from the cross burnsi × pipiens that produced 23 burnsi, 33 pipiens. Assume that the burnsi allele is dominant to the pipiens allele and that the burnsi parents are heterozygous. - With one degree of freedom, the chi-square value is less than 2.076 for a probability value of greater than 0.1, so the deviation between observed and expected was likely to occur by chance - Use a chi-square test to evaluate the fit of the observed numbers of progeny to the number expected from the cross burnsi × pipiens that produced 196 burnsi, 210 pipiens. Assume that the burnsi allele is dominant to the pipiens allele and that the burnsi parents are heterozygous - With one degree of freedom, the chi-square value is less than 0.2.706 for a probability value of greater than 0.1, so the deviation between observed and expected was likely to occur by chance - With the assumption that Schmid-type metaphyseal chondrodysplasia is rare, is this type of dwarfism inherited as a dominant or recessive trait and why? - The nearly one–to-one ratio seen in the offspring suggests it is likely inherited as a dominant trait, with the dwarf parent being heterozygous for the dwarf allele along with the normal parent being homozygous for the normal allele - Use a chi-square test to determine if the total number of children for these families (52 normal, 40 dwarfs) is significantly different from the number expected. Assume that the trait is dominant and that one parent is heterozygous for the dwarf allele and the other parent is homozygous for the normal allele - With one degree of freedom, the chi-square value is greater than 0.455 for a probability value of less than 0.5, so the deviation between observed and expected was likely to occur by chance. - Use a chi-square test to determine if the number of children in family C (1 normal, 6 dwarf) are significantly different from the numbers expected. Assume that the trait is dominant and that one parent is heterozygous for the dwarf allele and the other parent is homozygous for the normal allele - With one degree of freedom, the chi-square value is greater than 2.706 for a probability value of less than 0.1, so the deviation between observed and expected was likely to occur by chance - Use a chi-square tests to determine if the number of children in family D (6 normal, 2 dwarf) are significantly different from the numbers expected. Assume that the trait is dominant and that one parent is heterozygous for the dwarf allele and the other parent is homozygous for the normal allele - With one degree of freedom, the chi-square value is greater than 0.455 for a probability value of less than 0.5, so the deviation between observed and expected was likely to occur by chance - Give the expected numbers of progeny with each phenotype if the genes for pink- eye and albinism assort independently - 1/4 wild type, 1/4 wild-type fur and pink eyes, 1/2 albinos (because albinos with wild-type eyes are difficult to distinguish from albinos with pink eyes - Use a chi-square test to determine if the observed numbers of progeny fit the number expected with independent assortment - With two degrees of freedom, the chi-square value is greater than 10.597 for a probability value of less than 0.005, so the deviation between observed and expected was not likely to occur by chance - In the California poppy, an allele for yellow flowers (C) is dominant over an allele for white flowers (c). At an independently assorting locus, an allele for entire petals (F) is dominant over an allele for fringed petals (f). A plant that is homozygous for yellow and entire petals is crossed with a plant that is white and fringed. A resulting F1 plant is then crossed with a plant that is white and fringed, and the following progeny are produced: 54 yellow and entire, 58 yellow and fringed, 53 white and entire, and 10 white and fringed. Using a chi-square test to compare the observed numbers with those expected for the cross, what can you conclude in regard to whether the ratios observed occurred due to random variations - With three degrees of freedom, the chi-square value is greater than 12.838 for a probability value of less than 0.005, so the deviation between observed and expected was not likely to occur by chance - In the California poppy, an allele for yellow flowers (C) is dominant over an allele for white flowers (c). At an independently assorting locus, an allele for entire petals (F) is dominant over an allele for fringed petals (f). A plant that is homozygous for yellow and entire petals is crossed with a plant that is white and fringed. A resulting F1 plant is then crossed with a plant that is white and fringed, and the following progeny are produced: 54 yellow and entire, 58 yellow and fringed, 53 white and entire, and 10 white and fringed. Suggest an explanation for the results - The number of plants with the cc ff genotype is much less than expected, so perhaps this genotype is less viable than other genotypes - Dwarfism is a recessive trait in Hereford cattle. A rancher in western Texas discovers that several of the calves in his herd are dwarfs, and he wants to eliminate this undesirable trait from the herd as rapidly as possible. Suppose that the rancher hires you as a genetic consultant to advise him on how to breed the dwarfism trait out of the herd. What crosses would you advise the rancher to conduct to ensure that the allele causing dwarfism is eliminated from the herd? - All of above are correct - A geneticist discovers an obese mouse in his laboratory colony. He breeds this obese mouse with a normal mouse. All the F1 mice from this cross are normal in size. When he interbreeds two F1 mice, eight of the F2 mice are normal in size and two are obese. The geneticist then intercrosses two of his obese mice, and he finds that all of the progeny from this cross are obese. These results lead the geneticist to conclude that obesity in mice results from a recessive allele. A second geneticist at a different university also discovers an obese mouse in her laboratory colony. She carries out the same crosses as the first geneticist and obtains the same results. She also concludes that obesity in mice results from a recessive allele. One day, the two geneticists meet at a genetics conference, learn of each other's experiments, and decide to exchange mice. They both find that, when they cross two obese mice from the different laboratories, all the offspring are normal. However, when they cross two obese mice from the same laboratory, all the offspring are obese. Which of the following BEST explains their results? - Both obesity alleles are recessive but are located at different loci - Albinism is a recessive trait in humans. A geneticist studies a series of families in which both parents are normal and at least one child has albinism. The geneticist reasons that both parents in these families must be heterozygotes and that albinism should appear in 1/4 of the children of these families. To his surprise, the geneticist finds that the frequency of albinism among the children of these families is considerably greater than 1/4. Can you think of an explanation for the higher-than- expected frequency of albinism among these families - He is only looking at parents who have albino children, but heterozygous parents without albino children are being missed by the study - Two distinct phenotypes are found in the salamander Plethodon cinereus: a red form and a black form. Some biologists have speculated that the red phenotype is due to an autosomal allele that is dominant over an allele for black. Unfortunately, these salamanders will not mate in captivity; so the hypothesis that red is dominant over black has never been tested. One day a genetics student is hiking through the forest and finds 30 female salamanders, some red and some black, laying eggs. The student places each female and her eggs (about 20–30 eggs per female) in separate plastic bags and takes them back to the lab. There, the student successfully raises the eggs until they hatch. After the eggs have hatched, the student records the phenotypes of the juvenile salamanders, along with the phenotypes of their mothers. Thus, the student has the phenotypes for 30 females and their progeny, but no information is available about the phenotypes of the fathers. Explain how the student can determine whether red is dominant over black with this information on the phenotypes of the females and their offspring - The student will need to examine the colors and phenotypic ratios of the colors found in the offspring of each salamander. If a 3:1 phenotypic ratio of red to black is observed in the offspring of a red salamander, then the red allele is dominant over the black Chapter 4 - in the case of many organisms, sex is determined by specific sex chromosomes. In the case of most mammals, females are o XX. And homogrametic - in the case of a number of bird species, the male is homogametic rather than the female. This means that o a ZW individual is female - Human X and Y chromosomes: o have pseudo-autosomal regions that are homologous - Genic sex determination: o has been observed in a wide range of organism - In the case of the slipper shell Crepidula fornicata: o if the order is changed, the shells can change sex - Since individual humans do not need two X chromosomes (males, for example) or a Y chromosome, we can tolerate a large amount of variation in our sex chromosomes, with variants such as: o Turner's syndrome, with only a single X chromosome. - When a trait appears to be inherited differently in different sexes it is said to be o sex linked. - White eye color in Drosophila was discovered to be sex linked by Thomas Hunt Morgan, who observed that o reciprocal crosses produced different results, which is not true for most traits and the inheritance pattern depended on the sex of the individuals - Investigating the sex-linked trait white eyes in fruit flies, the unusual observation was made that only about 90% of the offspring followed the expected patterns. Morgan's student Bridges explained the new observations o by proposing a failure in meiosis, by developing the theory of nondisjunction., by analyzing the behavior of chromosomes - In humans, X-linked color blindness o affects men more often than women because it is on the X chromosome - With a Z-linked trait such as the cameo phenotype in peacocks, the trait o is more often observed in females than males because it is on the Z chromosome - The Y chromosome is believed to have evolved from the X chromosome by a series of steps, including all of the following EXCEPT o Actually, all of these are proposed steps in the evolution of the Y chromosome - Dosage of some genes, such as eye color, does not make a large difference phenotypically. Dosage of others can be very important, and, in order to balance dosages of genes on sex chromosomes and autosomes, all of the following mechanisms are employed EXCEPT o increasing the number of sex chromosomes. - Inactivation of X chromosomes by mammals results in all of the following EXCEPT: o males and females producing different amounts of protein from genes on the X chromosome. - Assume that a mutation occurs in the XIST gene of a XY male that makes the gene inactive. What would you expect would be the phenotypic consequences of this mutation for the male? - He would probably have no phenotypic consequences - In birds, females have which sex chromosomes? - ZW - In organisms with genic sex determination, sex is determined by - genes on chromosomes that do not differ between males and females - Dosage compensation is a mechanism that - equalizes the amount of protein produced by X-linked genes in the two sexes. - A man and a woman who both have normal vision have a daughter with the sex- linked recessive condition of red-green colorblindness. The daughter is also short and has folds of skin on the neck. A chromosome analysis of the daughter would likely reveal that she has which of the following chromosome constitutions? - XO - XY males inherit genes for an X-linked recessive trait from - their mother only. - Dosage compensation in human cells is achieved by - inactivating one X chromosome of females. - In mammals, each inactivated X chromosome forms a darkly staining body known as a body. - Barr - In the XX, XY system, males possess only a single X-linked allele and therefore are said to be for most X-linked loci. - hemizygous - How many active X chromosomes would be found in an individual with a XXYY chromosome constitution? - One - Traits encoded by genes located on the X chromosome are termed X- traits. - linked - Chromosomes that differ between males and females are called chromosomes. - sex - A woman who is heterozygous for the sex-linked condition of red-green colorblindness marries a man with normal vision. Which of the following would you not expect to observe among their possible children? - A son with normal vision and a daughter who is colorblind - In organisms with ZZ, ZW sex determination, males have which sex chromosomes? - ZZ - A triplo-X (XXX) individual has how many Barr bodies? - 2 - Fruit flies with XXY sex chromosomes and all other chromosomes normal in number have which sexual phenotype? - Female - In which of the following chromosome constitutions would you expect to find one Barr body in the nuclei of somatic cells - XXY - The patchy distribution of black and orange fur in tortoiseshell cats is caused by X - inactivation - Research suggests that the X and Y chromosomes evolved from a pair of - autosomes - In which sex-determining system is the male the heterogametic sex? - XX, XY, XX, XO - An individual with Turner syndrome has how many Barr bodies - 0 - Individuals with insensitivity syndrome are XY but have female external characteristics - androgen - A male with normal sex chromosomes has how many Barr bodies - 0 - In XX, XO sex determination, males have which sex chromosomes? - A single X chromosome - What is the probability that the first son born of a woman heterozygous for the sex- linked recessive condition of red-green colorblindness and a man with normal vision will be colorblind? - 1/2 - In which of the following chromosome constitutions would you expect to find one Barr body in the nuclei of somatic cells? - XXY - A man with a mutation of his Y chromosome marries a normal woman who does not carry this mutation. It would be expected that - all of their sons would inherit this mutation - Studies of rare white-eyed males in Drosophila crosses by demonstrated that the gene for white eyes is on the X chromosome and confirmed the chromosome theory of inheritance. - Bridges - DNA sequencing has revealed the presence of which feature on the human Y chromosome? - Eight large palindromes (sequences that read the same on both strands of DNA - When T.H. Morgan crossed the mutant male fruit fly with white eyes to normal females with red eyes, he found in the F1 offspring mostly - both males and females with red eyes - In biology, the sex (male or female) of an organism is defined in reference to its - phenotype - In species, male and female reproductive structures occur in different organisms. - dioecious - Nondisjunction occurs when - chromosomes fail to separate properly in meiosis - The process of dosage equalizes the amount of protein produced by X-linked genes in the two sexes - compensation - The term sex refers to an organism's sexual - phenotype - In which sex-determining system is the female the heterogametic sex - ZZ, ZW - A man with a hereditary skin condition has 10 children with a phenotypically normal woman who is homozygous for the normal allele: 5 of the children are normal boys and 5 are girls who all have the same skin condition as their father. Which of the following is the most likely genetic basis for the skin condition? - X-linked dominant - Fruit flies with a single X chromosome (XO) and all other chromosomes normal in number have which sexual phenotype - Male - Fruit flies with XX sex chromosomes and three haploid sets of autosomes (AAA) have which sexual phenotype? - Intersex - The fundamental difference between males and females across all organisms is the - size of the gametes: Males produce small gametes, and females produce larger gametes - Y-linked markers are - DNA sequences on the Y chromosome that vary among individual males - Sex-linked characteristics are characteristics that are - determined by genes on the sex chromosomes - Traits encoded by genes located on the Y chromosome are termed Y- traits. - linked - A bird that is heterozygous for a sex-linked trait is most likely to have which of the following chromosome constitutions? - ZZ - Sex in many turtles, crocodiles, and alligators is determined by - temperature during embryonic development - A man who is heterozygous for a sex-linked recessive condition such as red-green colorblindness is likely to have which of the following chromosome constitutions? - XXY - A cross is made between a female Drosophila heterozygous for the recessive alleles cn (cinnabar eye) and y (yellow body), also recessive, and a cinnabar male with normal body color. Among the female progeny the phenotypes were 1/2 wild type and 1/2 cinnabar. Among the male progeny the phenotypes were 1/4 yellow body, 1/4 cinnabar, 1/4 wild type, and 1/4 cinnabar and yellow body. From these data, it can be determined that most likely - y is sex-linked and cn is autosomal - The sex that produces two different types of gametes with respect to the sex chromosomes is called the sex. - heterogametic - Individuals with Turner syndrome most often have which sex chromosomes? - XO (a single X chromosome) - What is the probability that the first son born of a woman heterozygous for the sex- linked recessive condition of red-green colorblindness and a man with normal vision will be colorblind? - ½ - Individuals with the most common form of Klinefelter syndrome have which sex chromosomes? - XXY - In sequential , each individual animal is both male and female, but not at the same time - hermaphroditism - In the XX-XO sex determination system which of the following is true? - The presence of only a single X chromosome determines the male sex, while the presence of two X chromosomes determines the female sex - Individuals with the most common form of androgen insensitivity syndrome have which sex chromosomes - XY - In hum