Medical Genetics Test Bank Chapter 8 (Gene Mapping and Identification)

1- In one gene mapping technique, denatured DNA from metaphase chromosomes 1s hybridized with a radioactively labeled probe. This DNA 1s then exposed to film to reveal the approximate chromosomal location of the DNA in the probe. Which technique does this best describe??

A) Southern blotting

B) In situ hybridization

C) Somatic cell hybridization

D) Fluorescence in situ hybridization

E) Single strand conformation polymorphism (SSCP) analysis

... Answer is B)

2- Consider the table of LOD scores shown below for an autosomal dominant disease. The first line gives recombination frequencies, and each subsequent line represents the LOD score pattern found for a specific family. What phrase best describes this pattern??

A) Tight linkage

B) Allelic heterogeneity

C) Loose linkage

D) Linkage disequilibrium

E) Locus heterogeneity

... Answer is A)

3- Suppose you are attempting to find a disease-causing gene, and you have identified a number of families in which the disease is transmitted. If you have no knowledge of the gene product and no reasonable candidate locus, which of the following would be the first technique you would be most likely to use??

A) Linkage analysis

B) DNA sequencing

C) Single strand conformation polymorphism (SSCP) analysis

D) Denaturing gradient gel electrophoresis (DGGE)

E) Fluorescence in situ hybridization (FISH)

... Answer is A)

4- Now suppose that you do have a reasonable candidate locus for the disease you are studying. Which of the following would be least likely to contribute useful information??

A) DNA sequencing

B) Single strand conformation polymorphism (SSCP) analysis

C) Northern blotting

D) Denaturing gradient gel electrophoresis (DGGE)

E) Chromosome karyotype

... Answer is E)

5- Some autosomal recessive diseases have a high prevalence in large populations, even though they are often fatal (e.g., sickle cell disease in Africans, cystic fibrosis in Europeans). Which of the following is the most likely explanation for this phenomenon??

A) Inbreeding

B) High mutation rates in specific populations

C) Survival advantage in heterozygous carriers

D) Survival advantage in individuals who are normal homozygotes

E) None of the above mechanisms explain the pattern

... Answer is C)

6- Which of the following would you not expect to see im a typical multifactorial disorder??

A) Positive correlation between prevalence of the disorder in the population and sibling recurrence risk

B) Rapid decrease of recurrence risk with more remote degrees of relationship

C) Co-occurrence of the disorder in fathers and sons

D) Sibling recurrence risk of 50%

E) Higher concordance in monozygotic twins than in dizygotic twins

... Answer is D)

7- You would be likely to observe the lowest heritability score in?

A) Cystic fibrosis

B) Spina bifida

C) Cleft lip/palate

D) Mumps

E) Congenital heart disease

... Answer is D)

8- Familial hypercholesterolemia?

A) Can be caused by defects in receptor-mediated endocytosis

B) Is an important cause of inherited heart disease

C) Is an example of a disease in which gene therapy is being tested

D) A and B only

E) A, B, and C

... Answer is E)

9- Familial Alzheimer disease is characterized by?

A) Autosomal dominant transmission in some families

B) Locus heterogeneity

C) Population association with specific apolipoproteim E alleles

D) All of the above

E) None of the above

... Answer is D)

10- Which of the following is not true of schizophrenia??

A) Monozygotic twin concordance exceeds dizygotic twim concordance.

B) Gene mapping studies have shown linkage to specific polymorphic markers in some families.

C) A specific schizophrenia susceptibility gene has been cloned.

D) Adoption data indicate an increased risk of the disorder among the biological offspring of schizophrenic parents when the offspring are reared by normal parents.

E) Second-degree relatives of affected individuals have a lower risk of developing the disease than do first-degree relatives

... Answer is C)

11- Which of the following is an advantage of indirect genetic diagnosis??

A) Family data are not needed

B) Error due to recombination is not present

C) Uninformative matings do not present a problem

D) All of the above

E) None of the above

... Answer is E)

12- A neural tube defect (anencephaly or spina bifida) could be detected by?

A) Anmiocentesis

B) Chorionic villus sampling

C) Diagnosis of fetal cells in maternal circulation

D) In vitro fertilization diagnosis

E) All of the above

... Answer is A)

13- Which of the following is not currently a candidate for gene therapy??

A) Cystic fibrosis

B) Adenosine deaminase (ADA) deficiency

C) Lung cancer

D) Bipolar affective disorder

E) AIDS

... Answer is D)

14- Match each genetic disease with the most appropriate molecular or biochemical characteristic. Answers can be used more than once. *Serine protease inhibitor defect?

A) Obesity

B) Sickle-cell disease

C) Familial adenomatous polyposis coli

D) Tay-Sachs disease

E) Alpha-1 antitrypsin deficiency

... Answer is E)

15- Match each genetic disease with the most appropriate molecular or biochemical characteristic. Answers can be used more than once. *Hexosaminidase A deficiency?

A) Obesity

B) Sickle-cell disease

C) Familial adenomatous polyposis coli

D) Tay-Sachs disease

E) Alpha-1 antitrypsin deficiency

... Answer is D)

16- Match each genetic disease with the most appropriate molecular or biochemical characteristic. Answers can be used more than once. *Leptin mutations in mouse?

A) Obesity

B) Sickle-cell disease

C) Familial adenomatous polyposis coli

D) Tay-Sachs disease

E) Alpha-1 antitrypsin deficiency

... Answer is A)

17- Match each genetic disease with the most appropriate molecular or biochemical characteristic. Answers can be used more than once. *Interaction of gene product with beta-catenin?

A) Obesity

B) Sickle-cell disease

C) Familial adenomatous polyposis coli

D) Tay-Sachs disease

E) Alpha-1 antitrypsin deficiency

... Answer is C)

18- Match each genetic disease with the most appropriate molecular or biochemical characteristic. Answers can be used more than once. *Specific mutation in beta-globin gene?

A) Obesity

B) Sickle-cell disease

C) Familial adenomatous polyposis coli

D) Tay-Sachs disease

E) Alpha-1 antitrypsin deficiency

... Answer is B)

19- Mosaicisim is a frequent cause of survival to term?

A) Down syndrome

B) Trisomy 13

C) Trisomy 18

D) Klinefelter syndrome (47,X XY)

E) Turner syndrome (45,X)

... Answer is E)

20- Leading known genetic cause of mental retardation in the human?

A) Down syndrome

B) Trisomy 13

C) Trisomy 18

D) Klinefelter syndrome (47,XXY)

E) Turner syndrome (45,X)

... Answer is A)

21- Phenotype is seen only in males?

A) Down syndrome

B) Trisomy 13

C) Trisomy 18

D) Klinefelter syndrome (47,XXY)

E) Turner syndrome (45,X)

... Answer is D)

22- Which of the following can be used as vectors in somatic cell gene therapy??

A) Retrovirus

B) Liposome

C) Adenovirus

D) Adeno-associated virus

E) All of the above

... Answer is E)

23- Maternal serum alpha-fetoprotein levels can be used to screen for?

A) Turner syndrome

B) Neural tube defects

C) Klnefelter syndrome

D) Down syndrome

E) Band D

... Answer is E)

24- Which of the following 1s not a potential problem with somatic cell gene therapy??

A) Transient expression

B) Potential for oncogenesis as a result of random integration

C) Difficulties in regulating gene activity

D) Ethical concerns surrounding the permanent alteration of our genetic heritage

E) None of the above

... Answer is D)

25- Which of the following pertain(s) only to genes located on the same chromosome??

A) Linkage

B) Synteny

C) Linkage disequilibrium

D) Association

E) A.B, and C

... Answer is E)

26- Multifactorial inheritance can reliably be distinguished from single-gene inheritance by?

A) Differences in sibling recurrence risks, with single-gene recurrence risks always being higher

B) More rapid decline in recurrence risks in more remote relatives for multifactorial diseases

C) More pronounced differences in sex ratio for multifactorial diseases

D) For multifactorial diseases, sibling recurrence risk increases when there are more affected individuals in the family

E) Band D

... Answer is E)

27- Which of the following is not true about chromosome translocations?

A) They can lead to missing or duplicated chromosome material in offspring of translocation carriers

B) They can be helpful in mapping disease-causing genes

C) They can cause cancer when they occur in somatic cells

D) They are known to increase with advanced maternal age

E) B and D

... Answer is D)

28- Alcoholism?

A) is known to cluster in families

B) is linked to a polymorphism near the dopamine D2 receptor gene

C) is seen with increased incidence in the offspring of alcoholic parents, even when they are adopted by non-alcoholic parents

D) is seen with increased incidence in the offspring of non-alcoholic parents when they are adopted by alcoholic parents

E) A and C

... Answer is E)

1- Your class of 100 individuals has been typed for a 3-allele microsatellite polymorphism, and the following genotypes were obtained.

Genotype	Count
1,1	4
1,2	18
1,3	24
2,2	8
2,3	28
3,3	18

Based on these genotype counts, what are the gene frequencies of alleles 1,2, and 3?.

2- Suppose you are studying a complex multifactorial disease, and you find that the concordance rate for this trait in monozygotic twins is identical to that of dizygotic twins. What is the heritability of this disease?.

3- A boy has severe hemophilia A (X-linked recessive). His sister also has hemophilia, but her disease is much milder. What is the most likely explanation for this difference in severity?.

4- Women with Turner syndrome (45, X karyotype) sometimes reproduce. What is the risk of a 45, X karyotype in their offspring at conception?.

5- Consider the accompanying pedigree, in which an autosomal dominant disease-causing gene is segregating. Each family member has been typed for a linked 4- allele microsatellite (recombination frequency = 0.02). What is the risk that the offspring in generation III will inherit the disease-causing gene?.

6- In the accompanying pedigree, in which an autosomal recessive disease is segregating, each member has been typed for a closely linked 5-allele microsatellite polymorphism. The genotypes are shown in the autoradiogram. The disease genotype for individual 5 is shown. For individuals 6,7, and 8, indicate whether they are homozygous normal, heterozygous carrier, or homozygous affected..

7- The president of a mythical country has just been named in a paternity suit. The defendant (labeled WC in the autoradiogram), the mother (labeled ML), and the baby (labeled "Buddy") have each been typed for two VNTR systems, as shown in the autoradiograms below. Each of these VNTR systems has four alleles. For the first VNTR, the frequencies of alleles 1,2,3, and 4 in the general population are 0.2, 0.4, 0.3, and 0.1, respectively. For the second VNTR, the frequencies of alleles 1,2,3, and 4 are 0.1, 0.1, 0.2, and 0.6, respectively. Answer 2 questions: Does the autoradiogram indicate that WC could be the father of Buddy? What is the probability that another male in the general population could be the father of Buddy?.

8- In the accompanying pedigree, an autosomal dominant disease gene is being transmitted. Each family member has been typed for a 7-allele microsatellite polymorphism. Based on the genotypes in generation III, what is the recombination frequency for the disease locus and the microsatellite polymorphism?.

9- A large number of different mutations in the NF1 gene can cause neurofibromatosis type 1. Although NF1 has been cloned and sequenced, indirect genetic diagnosis is often used for this disease. Why?.

10- (essay) Describe and compare direct and indirect genetic diagnosis (use at least one disease example for each type of diagnosis). What are the advantages and disadvantages of each approach.

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