Osteoarthritis Susceptibility 2 (OS2) in humans is a sex-influenced trait that i

Question

Osteoarthritis Susceptibility 2 (OS2) in humans is a sex-influenced trait that is autosomal dominant in females and recessive in males. Sally does not have OS2. Her husband Frank also does not have OS2 but his father did. What proportion of Sally and Frank's children ane expected to have OS2? a. none of the females will have OS2: 1/2 the males will have OS2 b. all of the females will have OS2: 1/2 the males will have OS2 c. 1/2 the females will have OS2: none of the males will have OS2 d. 1/2 the females will have OS2: all of the males will have OS2 e. 1/2 the females will have OS2: 1/2 of the males will have OS2

Explanation / Answer

ans) Before going to the answer, first we need to look some aspect on the occurance pattern of the autosomal dominant and autosomal reccesive disease.

The condition of the autosomal dominant inheritance is:-

1) Trait does not skip generation.

2) An affected person mating with an unaffected person should produce approximately 50% affected offspring.

3) Distribution of the trait among the sexes should be equal.

4) transmitted by the either sexe3s.

The condition of the autosomal reccesive disease is:-

1) trait can skip generation.

2) an almost equal number of affected males and females.

3) if both the parents are affected then all the offspring are affected.

4) in most cases unaffected parents mating with the affected individual, all children are unaffected.

5) Most affected individual have unaffected parents.

Now from the given condition that the mother is unaffected and the disease is dominant in case of the females and recessive in case of the males. As her husband is not affceted but his father is affeceted. This means her husband is a carrier of the disease.. As her husband is not affceted to the disease so it can taken that her mother-in-law (her husband mother) may not be affeceted. Because if she was affeceted ( dominant in case of female) then there is a very much possibility of affecting her husband too. As the disease in autosomal recessive (for males) it has skip the generation, a condition for the autosomal disease.

Now we get a clear idea that her husband is a cerrier of the disease taken as " Aa" ( "a' denote the affected trait)

Sally (unaffeceted female ) is taken as "AA"

Now a punnet square will detemine the affect on the offspring.

From the punnet square it can be seen that 50% or 1/2 of the offspring are affected.

So, as the disease is autosomal disease so, it can be concluded that 50% of males and females can be affeceted.

Option - e will be the correct option.

Female / Male A a A AA Aa A AA Aa

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