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TEST BANK 2024 WITH 100% CORRECT ANSWERS A) Virus - correct answers . In somatic cell gene therapy, what type of vector is most commonly used to alter a specific set of an individual's somatic cells? a. Virus b. Bacteria c. RNA polymerase d. Recombinant DNA Travel along the single DNA strand, adding the correct nucleotide to the new strand - correct answers 2. In DNA replication, what does the enzyme DNA polymerase do? a. Travel along the single DNA strand, adding the correct nucleotide to the new strand b. Move along the double strand of DNA to unwind the nucleotides of the double helix c. Hold the double strand apart while the correct nucleotides are added to the strand d. Transport the double strand of DNA from the nucleus to the cytoplasm for protein formation C - correct answers How is transcription best defined? a. DNA polymerase binds to the promoter site on ribonucleic acid (RNA). b. RNA directs the synthesis of polypeptides for protein synthesis. c. RNA is synthesized from a DNA template. d. A base pair substitution results in a mutation of the amino acid sequence. ANS: B One of the most commonly used stains is Giemsa stain. By using banding techniques, chromosomes can be unambiguously numbered, and individual variation in chromosome composition can be studied. Missing or duplicated portions of chromosomes, which often result in serious diseases, also can be readily identified. The correct option is the only one that accurately describes the purpose of the Giemsa staining technique. - correct answers 4. What is the purpose of using a Giemsa staining technique on chromosomes? a. Permit the mitotic process to be followed and monitored for variations. b. Allow for the numbering of chromosomes and the identification of variations. c. Identify new somatic cells formed through mitosis and cytokinesis. d. Distinguish the sex chromosomes from the homologous chromosomes. ANS: B Other disorders can be detected with this procedure. These include most neural tube defects, which cause an elevation of alpha fetoprotein in the amniotic fluid, and hundreds of diseases caused by mutations of single genes. Cytochrome P-450 is useful in helping to formulate drug doses more precisely. DNA polymerase travels along the single DNA strand, adding the correct nucleotides to the free end of the new strand during DNA replication. Embryonic proteins are not involved in neural tube defects. - correct answers An amniocentesis indicates a neural tube defect when an increase in which protein is evident? a. Cytochrome P-450 b. Alpha fetoprotein c. DNA polymerase d. Embryonic proteins ANS: B Amniocentesis is recommended only for pregnancies known to have an elevated risk for a genetic disease or in women older than 30 to 35 years of age because of the slightly higher risk of fetal loss as compared to the general population. Having a chronic illness, previous in vitro fertilization, or late menarche are not reasons to have an amniocentesis. - correct answers 6. Amniocentesis is recommended for pregnant with what history? a. Have a history of chronic illness b. Have a family history of genetic disorders c. Have experienced in vitro fertilization d. Had a late menarche ANS: D Chorionic villus sampling consists of extracting a small amount of villous tissue directly from the chorion. This procedure can be performed at 10 weeks' gestation and does not require in vitro culturing of cells; sufficient numbers are directly available in the extracted tissue. Thus the procedure allows prenatal diagnosis at approximately 3 months' gestation rather than at nearly 4 months' gestation which is generally when amniocentesis is performed. Gene mapping and linkage analysis are not performed exclusively on women who are 10 weeks' - correct answers 7. What is the technique for prenatal diagnosis of chromosomal abnormalities at 10 to 12 weeks' gestation? a. Gene mapping b. Linkage analysis c. Amniocentesis d. Chorionic villus sampling ANS: B Aneuploidy is usually the result of nondisjunction, an error in which homologous chromosomes or sister chromatids fail to separate normally during meiosis or mitosis. Aneuploidy refers to cells that do not contain a multiple of 23 chromosomes. Polyploidy is when a cell has more than the diploid number of chromosomes, it is said to be a polyploid cell. Translocation refers the interchanging of genetic material between nonhomologous chromosomes. - correct answers 8. What is the term for an error in which homologous chromosomes fail to separate during meiosis or mitosis? a. Aneuploidy b. Nondisjunction c. Polyploidy d. Translocation ANS: B This child has Trisomy 21, also known as Down syndrome. These children typically present with IQs ranging from 25 to 70. The facial appearance is distinctive and exhibits a low nasal bridge, epicanthal folds, protruding tongue, and flat, low-set ears. Widely spaced nipples and edema of the newborn's feet are characteristic of Turner syndrome. The high-pitched voice and gynecomastia are characteristic of Klinefelter syndrome. - correct answers 9. A healthcare professional is assessing a child who has complete trisomy of the twenty-first chromosome. What findings does the professional relate to this condition? a. Widely spaced nipples, reduced carrying angle at the elbow, and sparse body hair b. An IQ of 25 to 70, low nasal bridge, protruding tongue, and flat, low-set ears c. High-pitched voice, tall stature, gynecomastia, and an IQ of 60 to 90 d. Circumoral cyanosis, edema of the feet, short stature, and mental slowness ANS: C Nondisjunction during the formation of one of the parent's gametes or during early embryonic development occurs in approximately 97% of infants born with Down syndrome. In approximately 90% to 95% of infants, the nondisjunction occurs in the formation of the mother's egg cell. Down syndrome is rarely caused by paternal nondisjunction. Robertsonian translocations are responsible for 3% to 5% of cases of Down syndrome. A high-pitched voice and gynecomastia are characteristic of Klinefelter syndrome. - correct answers 10. What is the most common cause of Down syndrome? a. Paternal nondisjunction b. Maternal translocations c. Maternal nondisjunction d. Paternal translocation ANS: C In Turner syndrome, a sex chromosome is missing, and the person's total chromosome count is 45. Characteristic signs include short stature, female genitalia, webbed neck, shieldlike chest with underdeveloped breasts and widely spaced nipples, and imperfectly developed ovaries. Children with Down syndrome have an IQ of 25 to 70, low nasal bridge, protruding tongue, and flat, low-set ears. Children with Cri du chat have a characteristic cry and other symptoms include low birth weight, severe intellectual disability, microcephaly (smaller than normal head size), heart defects, and a typical facial appearance. A high-pitched voice and gynecomastia are characteristic of Klinefelter syndrome. - correct answers 11. What syndrome, characterized by an absent homologous X chromosome with only a single X chromosome, exhibits features that include a short stature, widely spaced nipples, and webbed neck? a. Down b. Cri du chat c. Turner d. Klinefelter ANS: B A disorder in the chromosome (47, XXY karyotype) results in a disorder known as Klinefelter syndrome. Turner syndrome has a karyotype of 45, X. Down syndrome is caused by Trisomy 21. Fragile X syndrome is caused by microscopically observable breaks and gaps in the X chromosome. - correct answers 12. A person with 47, XXY karyotype has the genetic disorder resulting in which syndrome? a. Turner b. Klinefelter c. Down d. Fragile X ANS: B The fragile X syndrome is the second most common genetic cause of intellectual disability (after Down syndrome). Fragile X, Klinefelter, and Turner syndromes not observed with enough frequency are to be recognized as the second most common cause of intellectual disability. - correct answers 13. What is the second most commonly recognized genetic cause of intellectual disability? a. Down syndrome b. Fragile X syndrome c. Klinefelter syndrome d. Turner syndrome ANS: D When the heterozygote is distinguishable from both homozygotes, the locus is said to exhibit codominance. An example is the ABO blood group, in which heterozygotes having the A and B alleles express both of them as A and B antigens on their red cells (forming blood group AB). Blood types A, B, and O do not demonstrate codominance. - correct answers 14. What is the blood type of a person who is heterozygous, having A and B alleles as codominant? a. A b. B c. O d. AB ANS: D Affected heterozygous individuals transmit the trait to approximately one half of their children; however, because gamete transmission is subject to chance fluctuations, it is possible that all or none of the children of an affected parent may have the trait. Nevertheless, when large numbers of matings of this type are studied, the proportion of affected children closely approaches one half. - correct answers 15. A couple has two children diagnosed with an autosomal dominant genetic disease and asks the healthcare professional what the probability is that their next child will have the same genetic disease. What response by the professional is best? a. One sixth b. One fourth c. One third d. One half ANS: C In most cases of recessive disease, both parents of affected individuals are heterozygous carriers. - correct answers 16. When a child inherits a disease that is autosomal recessive, it is inherited from whom? a. Father b. Mother c. Both parents d. Grandparent ANS: B Expressivity is the extent of variation in phenotype associated with a particular genotype. If expressivity of a disease is variable, then the penetrance may be complete but the severity of the disease can vary greatly. A well-known example of variable expressivity in an autosomal dominant disease is type 1 neurofibromatosis. The penetrance of a trait is the percentage of individuals with a specific genotype who also exhibit the expected phenotype. An allele whose effects are observable is said to be dominant, while one whose effects are hidden is said to be recessive - correct answers 17. People diagnosed with neurofibromatosis have varying degrees of the condition because of which genetic principle? a. Penetrance b. Expressivity c. Dominance d. Recessiveness ANS: B The gene responsible for retinoblastoma has been mapped to the long arm of