Medical Genetics 4th Edition by Lynn B. Jorde -Test Bank

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Jorde: Medical Genetics, 4^th Edition

Chapter 5: Sex-linked and Nontraditional Modes of Inheritance

Multiple Choice

1. Sickle-cell disease is the result of a single nucleotide substitution that produces a single amino acid substitution. This is best described as a
2. frameshift mutation
3. nonsense mutation
4. splice-site mutation
5. missense mutation
6. none of the above

Answer: d

2. Which of the following is not true of imprinting?
3. It is often associated with methylation.
4. Diseases involving imprinting genes can result from either over-expression or under-expression of the gene product.
5. It can be specific to only certain tissues.
6. Imprinting results in differential expression of a gene, depending on the gender of the individual who expresses the disease.
7. Imprinting can affect multiple genes in a single chromosome region.

Answer: d

3. What is a likely explanation for the high prevalence of cystic fibrosis in European populations?
4. Most of the disease genes are hidden in heterozygotes.
5. The locus has a high mutation rate.
6. Many different mutations can cause cystic fibrosis.
7. Inbreeding is common among Europeans.
8. Heterozygotes may have an advantage because of increased resistance to typhoid fever.

Answer: e

4. In one form of familial isolated growth hormone deficiency, deletion of an exon of a gene on chromosome 17 alters the protein product. In heterozygotes, this protein product then binds with the normal protein product encoded by the normal copy of the gene on chromosome 17, disabling the normal growth hormone molecule. This is best described as an example of
5. dominant negative effect
6. haploinsufficiency
7. gain of function mutation
8. loss of function mutation
9. none of the above

Answer: a

5. Which of the following characterize adult polycystic kidney disease?
6. locus heterogeneity
7. gain of function mutations
8. 2-hit model of causation
9. a and b
10. a and c

Answer: e

6. The mutation that causes Huntington disease is best described as
7. a CAG repeat expansion that occurs in the 3′ untranslated region of the gene
8. a CAG repeat expansion that produces a protein that tends to form aggreagates in the nucleus of the cell
9. a CAG repeat expansion that leads to haploinsufficiency and thus neuronal death
10. a CAG repeat expansion that causes earlier onset of the disease in males than in females
11. all of the above

Answer: b

7. Which of the following is not a characteristic of hemochromatosis?
8. high prevalence in European populations
9. locus heterogeneity
10. pleiotropy
11. different penetrance in males and females
12. early diagnosis can lead to effective treatment and prevention

Answer: d

8. A phenotypically normal woman has had two children with trisomy 13. Which of the following scenarios would be least likely to result in this recurrence?
9. she is a germ-line mosaic for trisomy 13
10. she carries a Robertsonian translocation of chromosome 13 to chromosome 14
11. she carris a Robertsonian translocation of chromosome 21 to chromosome 14
12. she has had both children in her late 40s
13. she carries a Robertsonian translocation of chromosome 13 to chromosome 15

Answer: c

9. Which of the following is not a feature of Down syndrome?
10. hypotonia (poor muscle tone)
11. reduced IQ
12. association with elevated maternal age
13. increased risk of leukemia
14. cleft lip/cleft palate

Answer: e

10. Uniparental disomy in a live birth is caused by which of the following mechanisms?
11. trisomic conception followed by subsequent loss of the chromosome that was contributed in single copy by one parent.
12. triploid conception followed by subsequent loss of the extra set of chromosomes
13. fusion of an egg cell and a polar body, resulting in a conception with no paternal genetic contribution
14. monosomic conception followed by the gain of a chromsome
15. all of the above

Answer: a

11. X inactivation
12. involves activation of the XIST gene on the X chromosome that becomes inactive.
13. does not affect the entire inactivated X chromosome
14. is associated with methylation of the inactive X chromosome.
15. can lead to disease symptoms for an X-linked recessive disorder in a heterozygous female if the proportion of inactivated paternal and maternal chromosomes deviated strongly from 50/50.
16. all of the above

Answer: e