Huntington\'s disease is caused by a dominant allele in humans. Individuals homo

Question

Huntington's disease is caused by a dominant allele in humans. Individuals homozygous for the gene die in utero, and heterozygotes develop neurological symptoms in their 30s and 40s; the disease claims their lives within 10 or so years. Let H represent the allele for Huntington's and h the allele for healthv individuals. a. What are the genotypes and phenotvpes? b. What is the probability that an individual whose father died of Huntington's will also develop the disease? In the US, the prevalence of Huntington's is 0.0001. What is the frequency of the H allele? c.

Explanation / Answer

a.
Huntington's disease shows autosomal dominant inheritance pattern.
Dominant disease allele = D
Recessive WT allele = d

So, one D allele can cause disease.
Affected individuals = DD or Dd

DD individuals die in utero.
Dd individuals exhibit neurological symptoms in their 30s-40s.

b.
Father died of Huntington disease.
So, his genotype = Dd
Assuming that mother is dd
Parental cross: Dd X dd
Progeny: Dd dd
There is a 50% chance that the child can be affected.

c.
Prevalence of D allele in the US = 0.0001
= 1/10000
= 1 in 10000

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