What is the probability of disease expression in a. individual A? b. individual

Question

What is the probability of disease expression in

a. individual A?

b. individual B?

c. individual C?

d. individual D?

The pedigrees indicated here were obtained with three unrelated families whose members express the same completely penetrant disease caused by an autosomal dominant mutation that is linked at a distance of 10 cM from a marker locus with three alleles numbered 1, 2, and 3. The marker alleles present within each live genotype are indicated below the pedigree symbol. The phenotypes of the newly born labeled individuals-A, B, C, and D-are unknown 13 22 13 22 HTO 12 32 12 32 12 32 12 32 12 32 12 32

Explanation / Answer

Here the descried pedigree is showing autosomal dominant mutant syndrome chart where we need to identify the phenotypic expressions probability. Here the family pedigree analysis would give us the results that is useful in genetic counseling.

This autosomal dominant case is having the mutant genetic expression in their respective progeny, here we are to find the A, B, C, and D s disease expression probability.

We know that dominant conditions are expressed in having both parent a carrier, so 50% chance is there for each of them. Affected males and females have the equal probability of passing on their traits to their next generation. As the first generation is affected fathers and also is the carrier. So the individuals are carrying that genotype while showing their phenotypes as inheriting the mutant allele.

Half of the children’s or off springs are carrying the diseases allele an half do not, so here the probability would be calculated by 'Binominal Theorem'. Here in this each term representing a possible outcome, the exponents we use of 'a' is to represent the number of males and exponent of 'b' is used as number of females.

From the first chart the number of outcome is expressed from 2 males and 2 females- probability expression is

p = 10 a2 b2

= 10 (1/2)2 * (1/2)2

= 10 (1/2)4

= 10 / 16

= 5/8.

All other answers for the probability expression will be following the same pattern.

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