Genetics Final Exam UPDATED Exam
Questions and CORRECT Answers
Daughter cells produced in meiosis have - CORRECT ANSWER - half the number of
chromosomes as daughter cells produced in mitosis
What statement is true about the structure of DNA? - CORRECT ANSWER - the two
strands of a DNA molecule are held together by base pairing
Which of the following statements are true about double-standard DNA? - CORRECT
ANSWER -A+C=T+G
A+G=C+T
A/G = T/C
(C+A)/(G+T) = 1
In a standard deck of playing cards, four suits exist (red suits = hearts and diamonds, black suits
= spades and clubs). Each suit has 13 cards: Ace (A), 2, 3, 4, 5, 6, 7, 8, 9, 10, and the face cards
Jack (J), Queen (Q), and King (K). In a single draw, what is the probability that you will draw a
red card? - CORRECT ANSWER - 1/2
Which of the following is a step in translation that requires complementary base pairing? -
CORRECT ANSWER - Adding the correct amino acid to the growing polypeptide chain
How many genetically different eggs could be formed by a woman with the genotype Aa Bb Cc
Dd Ee FF? - CORRECT ANSWER - 32
Your sister is pregnant with triplets, each of which was produced by a different fertilization
event. What is the chance that 2 of her babies are male and one is female? - CORRECT
ANSWER - 3/8
,Three genes in fruit flies affect a particular trait, and one dominant allele of each gene is
necessary to get a wild-type phenotype. What phenotypic ratios would you predict among the
progeny if you crossed triply heterozygous flies? - CORRECT ANSWER - 27:37
Which of the following probabilities is correct regarding the progeny of a mating of an Ss RR
individual to an individual who is Ss Rr ? (A - indicates the the second allele is either dominant
or recessive.) Alleles of the two genes assort independently. - CORRECT ANSWER - S-
RR : 37.5%
Cystic fibrosis is a rare disease caused by homozygosity for a recessive allele, and characterized
by a build-up of mucus in the lungs and difficulty breathing. A woman whose maternal uncle had
the disease is trying to determine the probability she and her husband could have an affected
child. Her husband's sister died of the disease. Assuming the uncle and the sister are the only
family members who had the disease, what is the chance that the couple's first child will be
affected? - CORRECT ANSWER - 1/18
If a trait is controlled by two codominant alleles of one gene, what phenotypic ratio is expected
in the offspring of a mating of two heterozygotes? - CORRECT ANSWER - 1:2:1
In which of the following scenarios will Allele 1, a normally functional allele of a gene, be
dominant to Allele 2 in a heterozygote? - CORRECT ANSWER - Allele 2 is non-
functional and for this particular gene, as for most genes in diploid organisms, only one normally
functional allele is required in order to avoid having a mutant phenotype
In the cross Aa Bb Cc Dd X aa bb cc dd, assuming independent assortment, what fraction of the
progeny will resemble one or the other parent? - CORRECT ANSWER - 1/8
Two alleles of gene C control hair color in horses: C¹ and C². Horses homozygous for allele C¹
are red, heterozygotes are yellow, and C² homozygotes are cream. What type of allele interaction
is described? - CORRECT ANSWER - incomplete dominance
The pedigree that follows is showing the inheritance pattern of deafness, a heterogeneous trait, in
a family. What is the genotype of the individuals in generation V? What phenomenon occurs in
generation V? - CORRECT ANSWER - Aa Bb; Complementation
, Wild-type grapes are green. Two pure-breeding parental strains of grape plants are crossed:
green and yellow. The F1 have all green grapes, and the F2 plants are present in a 9 green : 7
yellow ratio. What are the genotypes of the yellow F2? - CORRECT ANSWER - A- bb, aa
B-, and aa bb
In some flowers, a purple pigment is synthesized from a red precursor pigment. In the absence of
all pigment, flowers are white. A pure-breeding plant with red flowers was crossed to a pure-
breeding plant with white flowers. All of the F1 plants had white flowers. The F1 plants were
crossed to each other, and the F2 consisted of 166 plants: 123 with white flowers, 32 with purple
flowers, and 11 with red flowers. How do these results suggest that flower color is determined? -
CORRECT ANSWER - The dominant allele of one gene masks the effect of a second
gene
Jeff's father has Huntington disease, which is caused by a rare autosomal dominant allele (H ).
Two-thirds of people with the dominant Huntington allele show no symptoms by age 50, and Jeff
is 50 and has no symptoms. Jeff's wife is is pregnant. What is that chance that Jeff's child will
have symptoms of Huntington disease by age 50? - CORRECT ANSWER - 1/15
Drosophila melanogaster has four pairs of chromosomes (including a pair of sex chromosomes).
Sperm from this species are formed by a meiotic process in which homologous chromosomes
pair and segregate but do not undergo crossing-over. How many genetically different kinds of
sperm could be produced by a Drosophila melanogaster male (XY)? - CORRECT
ANSWER - 16
In Drosophila, the recessive allele for forked bristles is sex-linked, and the recessive allele for
purple eyes is autosomal. The wild-type alleles are for straight bristles and red eyes, respectively.
A female, heterozygous for both pairs of alleles, is mated with a male with forked bristles and
purple eyes. What percentage of the daughters will have forked bristles and purple eyes? -
CORRECT ANSWER - 25%
Red-green color blindness is controlled by an X-linked gene in humans. The allele that causes
color blindness is recessive to the allele for normal vision. A man and woman both with normal
vision had color-blind fathers. If this man and woman have a child, what is the probability that
the child will be color blind? - CORRECT ANSWER - 1/4
Questions and CORRECT Answers
Daughter cells produced in meiosis have - CORRECT ANSWER - half the number of
chromosomes as daughter cells produced in mitosis
What statement is true about the structure of DNA? - CORRECT ANSWER - the two
strands of a DNA molecule are held together by base pairing
Which of the following statements are true about double-standard DNA? - CORRECT
ANSWER -A+C=T+G
A+G=C+T
A/G = T/C
(C+A)/(G+T) = 1
In a standard deck of playing cards, four suits exist (red suits = hearts and diamonds, black suits
= spades and clubs). Each suit has 13 cards: Ace (A), 2, 3, 4, 5, 6, 7, 8, 9, 10, and the face cards
Jack (J), Queen (Q), and King (K). In a single draw, what is the probability that you will draw a
red card? - CORRECT ANSWER - 1/2
Which of the following is a step in translation that requires complementary base pairing? -
CORRECT ANSWER - Adding the correct amino acid to the growing polypeptide chain
How many genetically different eggs could be formed by a woman with the genotype Aa Bb Cc
Dd Ee FF? - CORRECT ANSWER - 32
Your sister is pregnant with triplets, each of which was produced by a different fertilization
event. What is the chance that 2 of her babies are male and one is female? - CORRECT
ANSWER - 3/8
,Three genes in fruit flies affect a particular trait, and one dominant allele of each gene is
necessary to get a wild-type phenotype. What phenotypic ratios would you predict among the
progeny if you crossed triply heterozygous flies? - CORRECT ANSWER - 27:37
Which of the following probabilities is correct regarding the progeny of a mating of an Ss RR
individual to an individual who is Ss Rr ? (A - indicates the the second allele is either dominant
or recessive.) Alleles of the two genes assort independently. - CORRECT ANSWER - S-
RR : 37.5%
Cystic fibrosis is a rare disease caused by homozygosity for a recessive allele, and characterized
by a build-up of mucus in the lungs and difficulty breathing. A woman whose maternal uncle had
the disease is trying to determine the probability she and her husband could have an affected
child. Her husband's sister died of the disease. Assuming the uncle and the sister are the only
family members who had the disease, what is the chance that the couple's first child will be
affected? - CORRECT ANSWER - 1/18
If a trait is controlled by two codominant alleles of one gene, what phenotypic ratio is expected
in the offspring of a mating of two heterozygotes? - CORRECT ANSWER - 1:2:1
In which of the following scenarios will Allele 1, a normally functional allele of a gene, be
dominant to Allele 2 in a heterozygote? - CORRECT ANSWER - Allele 2 is non-
functional and for this particular gene, as for most genes in diploid organisms, only one normally
functional allele is required in order to avoid having a mutant phenotype
In the cross Aa Bb Cc Dd X aa bb cc dd, assuming independent assortment, what fraction of the
progeny will resemble one or the other parent? - CORRECT ANSWER - 1/8
Two alleles of gene C control hair color in horses: C¹ and C². Horses homozygous for allele C¹
are red, heterozygotes are yellow, and C² homozygotes are cream. What type of allele interaction
is described? - CORRECT ANSWER - incomplete dominance
The pedigree that follows is showing the inheritance pattern of deafness, a heterogeneous trait, in
a family. What is the genotype of the individuals in generation V? What phenomenon occurs in
generation V? - CORRECT ANSWER - Aa Bb; Complementation
, Wild-type grapes are green. Two pure-breeding parental strains of grape plants are crossed:
green and yellow. The F1 have all green grapes, and the F2 plants are present in a 9 green : 7
yellow ratio. What are the genotypes of the yellow F2? - CORRECT ANSWER - A- bb, aa
B-, and aa bb
In some flowers, a purple pigment is synthesized from a red precursor pigment. In the absence of
all pigment, flowers are white. A pure-breeding plant with red flowers was crossed to a pure-
breeding plant with white flowers. All of the F1 plants had white flowers. The F1 plants were
crossed to each other, and the F2 consisted of 166 plants: 123 with white flowers, 32 with purple
flowers, and 11 with red flowers. How do these results suggest that flower color is determined? -
CORRECT ANSWER - The dominant allele of one gene masks the effect of a second
gene
Jeff's father has Huntington disease, which is caused by a rare autosomal dominant allele (H ).
Two-thirds of people with the dominant Huntington allele show no symptoms by age 50, and Jeff
is 50 and has no symptoms. Jeff's wife is is pregnant. What is that chance that Jeff's child will
have symptoms of Huntington disease by age 50? - CORRECT ANSWER - 1/15
Drosophila melanogaster has four pairs of chromosomes (including a pair of sex chromosomes).
Sperm from this species are formed by a meiotic process in which homologous chromosomes
pair and segregate but do not undergo crossing-over. How many genetically different kinds of
sperm could be produced by a Drosophila melanogaster male (XY)? - CORRECT
ANSWER - 16
In Drosophila, the recessive allele for forked bristles is sex-linked, and the recessive allele for
purple eyes is autosomal. The wild-type alleles are for straight bristles and red eyes, respectively.
A female, heterozygous for both pairs of alleles, is mated with a male with forked bristles and
purple eyes. What percentage of the daughters will have forked bristles and purple eyes? -
CORRECT ANSWER - 25%
Red-green color blindness is controlled by an X-linked gene in humans. The allele that causes
color blindness is recessive to the allele for normal vision. A man and woman both with normal
vision had color-blind fathers. If this man and woman have a child, what is the probability that
the child will be color blind? - CORRECT ANSWER - 1/4
