Medical Genetics Test Bank Chapter 1 (Background and History)

1- Achondroplasia has a high mutation rate. This is most likely the result of ?





... Answer is D)
2- The effect of mutations in the SHOX gene would best be described as?





... Answer is A)
3- Which of the following mechanisms is known to cause Prader-Willi syndrome??





... Answer is C)
4- Suppose you have established that a disease gene is closely linked to a marker whose location is known. Which of the following would not be useful in defining the disease gene's location??





... Answer is C)
5- Which of the following is least likely to be seen in a patient with Huntington disease?





... Answer is C)
6- Which of the following is not a characteristic of osteogenesis imperfecta?





... Answer is D)
7- In which of the following diseases are dominant negative mutation effects seen?





... Answer is D)
8- Which of the following is not true of Fragile X syndrome?





... Answer is D)
9- "Which of the following diseases follow(s) a "2-hit model?





... Answer is E)
10- The recurrence risk for trisomy 13 is increased by?





... Answer is E)
11- Which of the following is not correct about the XIST gene?





... Answer is D)
1- Your class, which has 100 individuals, has been typed for a locus that has three possible alleles, labeled 1, 2, and 3. The genotypes and their counts are:Based on these genotype counts, which is the gene frequency of allele 1?

1,1

10

1,2

5

1,3

15

2,2

20

2,3

20

3,3

30



2- If an X-linked recessive disorder affects approximately 1/1,000,000 females (all homozygotes) in a population, what is the expected frequency of affected males in the population?.

3- Two individuals who both have achondroplasia (autosomal dominant disorder) mate. What is the occurrence risk for this disorder in their offspring? .

4- Suppose that you have done a carrier test for PKU (autosomal recessive disorder) in a population, and you discover that the heterozygote carrier frequency is 1/500. Based on this information, what proportion of the population will be affected with PKU? (Note: your answer does not have to be exact.).

5- A woman with an X-linked dominant disorder mates with a phenotypically normal male. On average, what proportion of this couple's daughters will be affected with the disorder?.

6- A woman who is a heterozygous carrier of an X-linked recessive disease gene mates with a phenotypically normal male. The disease gene has a penetrance of 80%. On average, what proportion of this couple's sons will be affected with the disorder?.

7- In the accompanying pedigree, a man is affected with tyrosinase-negative oculocutaneous albinism (autosomal recessive). Based on this information alone, what is the probability that his grandson (labeled A) and his great-granddaughter (labeled B) are both heterozygous carriers of the albinism gene? 

8- A woman has an autosomal dominant form of postaxial polydactyly. Assuming that you have not examined any other family members to determine whether they have postaxial polydactyly, what is the probability that her second cousin (labeled A in the pedigree) is also affected with this fully penetrant disorder?

9- Discuss the concept of pleiotropy. Use at least two disease examples to illustrate the concept. (This answer should require no more than about five sentences.).

10- Hereditary diseases often present with no previous family history of the disorder. Briefly describe three situations in which you would be most likely to observe a genetic disorder for which there is no previous family history of the disease phenotype (three brief sentences should be sufficient). .

11- Match the pedigree with the most likely mode of inheritance. Note that complicating factors, such as reduced penetrance, may be present. Assume that the gene frequency of the disorder in the general population is very low. These answers may be used more than once.?





... Answer is D)
12- Match the pedigree with the most likely mode of inheritance. Note that complicating factors, such as reduced penetrance, may be present. Assume that the gene frequency of the disorder in the general population is very low. These answers may be used more than once?





... Answer is A)
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