The woman marked with a question mark is your friend. Knowing that you are takin

Question

The woman marked with a question mark is your friend. Knowing that you are taking Genetics, she comes to ask you for advice: she wants to have children, but is afraid that they will be sick with the disease. Her husband and her mother have no family history of HD. What is the probability that she is sick? What is the probability that her children will be, without knowing her own status regarding the disease?

P (friend sick) = 1; P (child sick) = ½

P (friend sick) = 0; P (child sick) = 0

P (friend sick) = ¼ ; P (child sick) = 1/16

P (friend sick) = ½ ; P (child sick) = ¼

Explanation / Answer

Answer: P (friend sick) = ½ ; P (child sick) = ¼

Explanation:

Huntington disease (HD) is inherited in an autosomal dominant manner.

In autosomal dominant inheritance, only one copy of a disease allele is necessary for an individual to be susceptible to expressing the phenotype.

Male (Hh) x Female (hh)

offsprings= Hh, Hh, hh, hh

1/2 or 50% of offsprings suffer from HD

Since ½ or 50% of the offsprings are females, ½ or 50% of female offsprings could suffer from HD

Therefore the friend in question has ½ chances of suffering from HD, her children ½ x ½ = ¼

P (friend sick) = ½ ; P (child sick) = ¼

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