Medical Genetics Test Bank Chapter 6 (Clinical Cytogenetics: The Chromosomal Basis of Human Disease)

1- Which of the following is not true od the trinucleotide repeat expansions that cause the neurodegenerative disorders Huntington disease and the spmocerebellar ataxias??





... Answer is A)
2- Segmental neurofibromatosis, in which disease features are seen in only part of the body, would best be described as?





... Answer is D)
3- Which of the following features is nof true of achondroplasia??





... Answer is E)
4- Which of the following is true of the Utah population??





... Answer is D)
5- In which of the following chromosome abnormalities is mosaicism most likely to be seen??





... Answer is D)
6- Wich of the following best explains variable expression in mitochondrial diseases??





... Answer is C)
7- Which of the following would be most likely to produce an imbalance in the amount of essential genetic material in the carrier??





... Answer is E)
8- Which of the following statements regarding chromosome abnormalities is true??





... Answer is A)
9- Which of the following conditions is most compatible with survival to term??





... Answer is E)
1- A population has been screened for mutations in the cystic fibrosis (autosomal recessive) gene using DNA testing. The test shows that 1/100 individuals in this population are heterozygous carriers of a cystic fibrosis (CF) mutation. Based on this figure, what is the expected proportion of affected individuals in this population?.

2- : Continuing question 1, if a known CF carrier in this population mates with somebody in the general population, what is the probability that the couple will produce a child affected with cystic fibrosis?.

3- Imagine that the known carrier in question 2 mates with his first cousin. What is the probability that this couple will produce a child affected with cystic fibrosis?.

4- You (or your significant other) have been identified as the culprit in a paternity suit. DNA testing has been performed to establish whether or not you are the father. Four VNTR loci were tested for you, the mother, and the baby in question. Unfortunately for you, the baby's alleles and your match for all four loci. The frequencies of these alleles in the general population are .05, .01, .01, and .02. What is the probability that somebody else in the general population could be the father of the baby?.

5- A woman has had two sons who are affected with Duchenne muscular dystrophy (X-linked recessive). She also has two normal sons, and there is no other family history of the disease. This woman also has muscle weakness in her legs. What is the likely explanation for her muscle weakness?.

6- Consider two linked loci, labeled A and B. Each locus has two alleles, labeled 1 and 2. The frequencies of the alleles in a population are: A1 = 0.6, A2 = 0.4, B1 = 0.7, B2 = 0.3. If there is linkage equilibrium between these two loci in the population, what is the expected frequency of chromosomes carrying a combination of the A1 and B2 alleles?.

7- In the accompanying pedigree, each individual has been assayed for a microsatellite repeat polymorphism that is known to be linked to an autosomal dominant disorder that is being transmitted in this family. The polymorphism has six alleles, labeled 1,2,3,4,5, and 6. The genotypes in this family are shown in the autoradiogram. Based on the genotypes of the offspring in generation III, what is the recombination fraction for the disease locus and the linked microsatellite system?.

8- Consider the accompanying pedigrees, in which an autosomal dominant disease is segregating. Based on the genotypes in generation III, what is the LOD score for the hypothesis that the recombination fraction for the disease locus and the marker locus (with 4 alleles, 1,2,3, and 4) is zero?.

9- A somatic cell hybridization panel is shown below. It indicates which clones yielded a positive hybridization signal for a DNA segment from a gene we wish to map. Based on the patterns in the hybridization panel, on which chromosome is the DNA segment located?.

10- The accompanying pedigree shows the mating of two individuals who are both heterozygous carriers of mutations that can cause Wilson Disease, an autosomal recessive disorder of copper metabolism. The parents and their three offspring have each been typed for a closely linked microsatellite polymorphism. Based on the autoradiogram, what is the genotype of individual 5 (i.e., normal homozygote, heterozygote, or affected homozygote)?.

11- (brief essay). In the family shown below, several females have been diagnosed with breast cancer (the mother in generation I has died). Two of the females have been tested for mutations in the BRCA1 gene on chromosome 17, and both of them have mutations in the gene. Yet a linkage analysis performed on the entire family yields a negative LOD score for linkage between a linked marker (r = .03) and breast cancer in this family. List two possible explanations for this finding. (2-3 sentences should be sufficient.).

12- (essay). Describe amniocentesis, chorionic villus sampling, and in vitro fertilization diagnosis, discussing the relative advantages and disadvantages of each procedure..

13- The autoradiogram shown here most likely represents variation at which type of system??





... Answer is A)
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