Cystic fibrosis is a hereditary disorder caused by a recessive mutation. in a previous marriage, jim had a child with cystic fibrosis, though neither jim nor his first wife had the disease. jim is now married to martha, who had a brother that died of cystic fibrosis. though martha does not have the disease, she found out that she is a carrier. what is the probability that jim and martha will have a baby with cystic fibrosis?

Question

Biology

Mohamed Stout

2 July, 03:51

Cystic fibrosis is a hereditary disorder caused by a recessive mutation. in a previous marriage, jim had a child with cystic fibrosis, though neither jim nor his first wife had the disease. jim is now married to martha, who had a brother that died of cystic fibrosis. though martha does not have the disease, she found out that she is a carrier. what is the probability that jim and martha will have a baby with cystic fibrosis?

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Wade · Answer 1

1) dа ta:

dominant allele - A

recessive allele - a

Heterozygotic: Aa (only carries the allele)

Homozygotic recessive: aa (expresses the disease)

Homozygotic dominant: AA (doesn't carry or expresses the disease)

2) The first cross between Jim and his first wife originated a offspring with

cystic fibrosis. That offspring has the genotype aa and for that to happen both parents need to be a least carriers or express the disease. The exercise rules out the second case, which makes Jim a carrier.

3) Now between Jim and Martha:

From the previous step, we already found that jim is a carrier and the exercise also tells us that Martha is one too. So, their genotype is: Aa.

The cross: Aa x Aa

The probability:

1/4 aa = 25%

2/4 = Aa

1/4 - AA

the probability of having a baby with cystic fibrosis is 25%