Question

A genetic trait is inherited via the Y chromosome such that for a father with the trait, his male offspring have a 25% chance of inheriting it but his female offspring cannot inherit it. Suppose that in a certain population, 40% of offspring are male and offspring genders are independent events. For a father with the trait who has two offspring, what is the probability that the older offspring has the trait and the younger offspring does not?

Answer 1

0.09

Step-by-step explanation:

let us define these events as

O = older

Y = younger

Prob(O) = 40% offspring x 25% chance of inheritance

= 0.4x0.25

= 0.1

P(Y') = 40% offspring x (1-25%) +(1-40%)x1

= 0.4x0.75 + 0.6x1

= 0.3+0.6

= 0.9 this is the probability of having the trait.

Probability that older offspring has trait but younger does not have it

Prob(O n Y') = prob(O) x Prob(Y')

= 0.1x0.9

= 0.09