Question

URGENT PLEASE

!!!!!!!!!!!!!!!!!!!!!!!!!
Bill and Jenny have three children. One of their children has cystic fibrosis, which is a recessive disorder (cc). Neither of the parents has the disorder.



Part A: Explain how it is genetically possible that one of their children has cystic fibrosis. (3 points)




Part B: What are the odds that each child produced by Bill and Jenny could have cystic fibrosis? (1 point)

Answer 1

A ) Because their parents are heterozygous recessive of cystic fibrosis.

B) there is a 25% chance that child produced by them has the disease !!

Answer 2

Part A: Both the parents must be the carrier of the diseases that is, Cc.

Part B: one out of four or 25 percent chances are there that their offspring would have cystic fibrosis.

As cystic fibrosis is an autosomal recessive disorder, the individual needs to carry two copies of the recessive allele that is, homozygous recessive (cc).

It is stated that neither of the parents has the disorder but their offspring show the phenotype, then both the parents must be the carrier of the disorder that is, both must heterozygous (Cc).

The offspring produces by this cross can have three types of genotypes CC, Cc, cc in 1:2:1.

Thus, only one out of four would show the disease.