45. A couple wants to know the probability that their ex. pected child will suff

Question

45. A couple wants to know the probability that their ex. pected child will suffer from split-hand deformity which affects the prosetve fathernd which affects the prospective father, who is indicated by an arrow in the pedigree shown. (The arrow mean that he is the proband- the person in the family who first brought the disorder to the attention of medical professionals.) This trait, shown in the following photo, is rare in the population, and the prospective parents are not related to each other. © Maria Platt-Evans/Science Source

Explanation / Answer

In this chart the affected person or proband have normal parents which point towards that the deformity might be autosomal recessive. As in autosoal recessive disorder, parents seems to be normal for affected children. Person who is heterozygous for the disorder will show nomal phenotype.

Thus if the normal genotype is AA, affected genotype will be aa and carrier will be Aa.

Now, the person with whom the proband is married can have the genotype wither Aa or AA. depending on this the probability of their children to show the deformity will be

Option: I

aa ( father) X Aa (mother)

a

a

A

Aa

Aa

a

aa

aa

The child will have the genotype either Aa or aa. So there is 50% chance of having the deformity.

Option: II

aa (father ) X AA (mother)

a

a

A

Aa

Aa

A

Aa

Aa

The child will have the genotype Aa, so the child will be carrier but will show no deformity.

a

a

A

Aa

Aa

a

aa

aa

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