Huntington’s disease is a rare neuro-degenerative disease which appears late in
ID: 186166 • Letter: H
Question
Huntington’s disease is a rare neuro-degenerative disease which appears late in life and causes motor function issues and dementia. The following pedigree shows the progression of the disease through a family through multiple generations. What can you say about the genetic aspect of the disease?
Huntington's disease is a rare neuro-degenerative disease which appears late in life and causes motor function issues and dementia. The following pedigree shows the progression of the disease through a family through multiple generations. What can you say about the genetic aspect of the disease? (1 point) Female with HD (Hh) O Normal Female (hh) Male with HD (Hh) Normal Male (hh) a-it is caused by an autosomal dominant allele b. t is caused by an X-linked recessive allele OCIt is caused by an autosomal recessive allele Od.t is Y-linked (carried on the Y chromosome)Explanation / Answer
Ans. Option [a] It is caused by an autosomal dominant allele [H]
Reason : * The gene cannot be present on the Y chromosome because the mother [female] is the carrier and two children , a male and a female ,are carriers of the defective gene in the first generation.
* It cannot be present on the X chromosome either because for the second generation the affected child has recieved X chromosome from a normal mother and Y chromosome from affected father.
This points to the fact that the gene for the disease is not present on the sex chromosomes.
The child in the next generation may or may not be affected by the defective gene as during spermatogenesis in the affected father, the gene may go to any autosome at 'crossing over' during meiosis.
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