1. Huntington\'s Disease is a fatal syndrome caused by a mutation in the HD gene

Question

1. Huntington's Disease is a fatal syndrome caused by a mutation in the HD gene. The disease has an average age of onset of 35 and the majority of individuals that are affected are heterozygotes. What is the probability that a 25 year old woman with no symptoms and who is the daughter of a man that has HD and a mother who does not will have a child that will have the mutant HD allele?

A. 75%

B. 50%

C. 25%

D. 100%

2. According to the Law of Segregation allele segregation into gametes is

A. based on whether the individual is male or female

B. based on whether the allele is dominant or recessive

C. random

D. based on whether the individual is homozygous or heterozygous

Explanation / Answer

1. (c)25%

The chances for the 25 year old woman to have HD is 50% due to the fact that this father is affected by HD and the mother is not having HD. Thus if she has a daughter with a male without HD, then the daughter will have 25% chance of having HD. This can be easily seen through test cross process.

2. Answer (C)
Mendel's law of segregation states clearly that  allele pairs separate or segregate during gamete formation, and randomly unite at fertilization.

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