Question

Suppose that a disease is inherited via a dominant mode of inheritance and that only one of the two parents is affected with the disease. The implications of this mode of inheritance are that the probability is 0.3 that any particular offspring will get the disease, and is 0.15 that all the offspring will get the disease.
A) What is the probability that in a family with two children, both siblings are affected?B) What is the probability that exactly one sibling is affected?C) What is the probability that neither sibling is affected?D) Suppose the older child is affected. What is the probability that the younger child is affected?

Answer 1

Answer:

Step-by-step explanation:

A ) Let p be the probability of getting affected . Probability of not getting affected be q

p = .3 , q = .7

If n be the member of family , probability that x children will be affected will be given by the expression

p(x) = ⁿCₓ pˣqⁿ⁻ˣ

n = 2 , x=2

p(2) = ²C₂ .3².7²⁻²

= 1 x .09 x 1 = .09

B )

p(1) = ²C₁ .3¹.7²⁻¹

=  2 x .3 x .7

= .42

C ) x = 0

p (0) = ²C₀ .3⁰.7²⁻⁰

=  1 x 1 x .49

= .49

D ) Let A be the probability that older child is affected and B be the probability that younger child is affected

P( A /B ) = P(A∩B) / P(B )

= .09 / .42

= .214