Question

In: Biology

Huntington disease is a rare neurodegenerative human disease determined by an autosomal dominant allele. (Because it...

  1. Huntington disease is a rare neurodegenerative human disease determined by an autosomal dominant allele. (Because it is a rare disease, homozygous individuals are also rare.) The disorder is typically a late onset disease with symptoms appearing after the age of 30. A young man has learned that his father has developed the disease.

  1. What is the probability that the young man will also develop the disease?
  1. What is the probability that a child of the young man develops the disease?

Solutions

Expert Solution

Since, Huntington disease is determined by an autosomal dominant allele, it can be expressed both in homozygous as well as heterozygous condition.

a)

In the given data, the phenotype, i.e., occurrence of Huntington disease in the young man's father only was given, but not his genotype.

Since, Huntington's disease can occur both in homozygous as well as in heterozygous condition, the young man's father can be homozygous dominant or heterozygous dominant for the given condition.

If his father is homozygous dominant for the occurrence of Huntington's disease, then the probability of the occurrence of Huntington's disease in the young man is 100% as this disease is determined by an autosomal dominant allele.

If his father is heterozygous dominant for the given condition, then there is 50% probability that the young man gets the disease.

b)

If the young man gets the disease determined by homozygous dominant allelic pair, then the probability of his son getting the disease is 100% and if the young man's disease is determined by heterozygous dominant allele, then the probability of occurrence of Huntington's disease in his son is only 50.


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