The manifestation of a disease is not always absolute. Not all affected people w
ID: 97596 • Letter: T
Question
The manifestation of a disease is not always absolute. Not all affected people will show the same range of symptoms. The genetic concept underlying this phenomenon is often referred to as a. co-dominance b. epistasis c. expressivity d. penetrance e. none of the above In a cross of MmQq x MmQq. the phenotypes of the mmqq and M-qq offspring are identical. This indicates which of the following phenomena? a. M is recessively epistatic to Q b. Q is dominant to M c. Q is dominantly epistatic to M d. Q is recessively epistatic to M e. M is dominantly epistatic to Q Genes ho and dp are 9.0 map units apart, and genes dp and da are 26.3 map units apart. What is the probability of a double crossover in these regions? A. 1.3% B. 2.4% C 3.4% D. 4.5% E. 5.6% A genetic defect in humans results in the absence of sweat glands in the skin. Men with this defect are lacking sweat glands all over their bodies, but in women it is usually expressed in a peculiar way: A woman with this defect typically has small patches of skin with sweat glands and other patches without sweat glands. In women, the pattern of sweat-gland distribution can best be explained by what phenomenon? a. RNA splicing b. a mutation c. a malfunctioning operon d. epistasis e. X chromosome inactivation Four genes (A, B, C, and D) are on the same chromosome. The recombination frequencies are as follows: A-B: 19%: B-C: 14%: A-C: 5%: B-D: 2%: A-D: 21%: C-D: 16%. Based on this information, which sequence of genes is correct? a.ACDB b. ACBD c. ABDC d. ADBC e. ABCDExplanation / Answer
correct answer is D
that is penetrance.
explaination
penetrance in genetics is the proportion of individuals carrying a particular variant of a gene that also express an associated trait.
in medical genetics, the penetrance of a disease causing mutation is the proportion of individuals with the mutation who exhibit clinical symptoms.
for example
retinoblastoma is a cancer of retina which primarily occur in children and is caused by the mutation in the Rb gene.
interestingly , not all the children who carry this mutation suffer from retinoblastoma.
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