In genetics, what does it mean if a person is a "Carrier"? You meet two people who are planning...

Question:

In genetics, what does it mean if a person is a "Carrier"? You meet two people who are planning on having children, but they are concerned about their chances of their child having cystic fibrosis. Cystic fibrosis is a recessive trait. They are normal and their parents are all normal, but both of them have brothers or sisters with cystic fibrosis. Use punnett squares to help give the possible chances of having a child with cystic fibrosis. Does the child's gender make any difference?

CFTR mutation

Cystic fibrosis transmembrane conductance regulator is a type of protein that lies in the cell membrane. This is coded by the CFTR gene. When there is a CFTR mutation, this results in cystic fibrosis.

Answer and Explanation:

1) A carrier is some one who carries a certain variant of a trait but does not express it. These people are usually heterozygous.

2) If both of their brother and sisters have CF we know, at least that both of their parents were heterozygous meaning they both carry the recessive CF allele. This does not necessarily mean that the couple planning to have the child does. We will use the letters "F" and "f" to represent the alleles for CF. Both of the parents of the couple are heterozygous so the cross of each parent is Ff x Ff.

F f
F FF Ff
f Ff ff

3) The couple could have the following genotypes if both their parents were heterozygous. These genotypes are FF and Ff. If both of the people in the couple were heterozygous, they would have a 25% chance of having a child with CF. That would be the only allelic combination that could result in CF. Other than that, there would be a 0% chance of having a child with CF.

4) The child's gender would not make a difference because CF is inherited on the autosomes and not the sex chromosomes.


Learn more about this topic:

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Cystic Fibrosis: Cause, Progression, and Treatment

from Pathophysiology Textbook

Chapter 9 / Lesson 16
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