Question

. A man’s grandfather has galactosemia, a rare autosomal recessive disease caused by the inability to process galactose, leading to muscle, nerve, and kidney malfunction. The man married a woman whose sister had galactosemia. The woman is now pregnant with their first child.

**b.** **What is the probability that this
child will have galactosemia?**

**c.** **If the first child does have
galactosemia, what is the probability that a second child will have
it?**

Answer #1

The probability of the man getting the defected allele is 1/4

1/2 probability of the child being a male and another 1/2 for him to acquire the disease allele

The woman must be atleasr a carrier if her sister suffered from the disease i.e. the probability of her having the allele is 1/2

The probability For both these to produce a child with the disease is 1/4*1/2=1/8

C. The probability of the disease occurrence will remain the same irrespective of the order and sex.

In humans, the disease galactosemia is inherited as a
rare autosomal recessive trait in a simple
Mendelian manner. A normal woman whose father had galactosemia
intends to marry a normal man whose grandfather had galactosemia.
What is the probability that their first child will have
galactosemia?
A. 1/2
B. 1/8
C. 1/16
D. 1/4
E. 0
Correct Answer: B. 1/8
Can you explain why?

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