Baldness is a dominant trait that is influenced by an individual's sex. A man will become bald if he has the genotype BB or Bb. A man who is bb will not become bald. A woman will have thinning hair, but not become totally bald, if she is BB. A woman will not become bald, or have thinning hair, if she is Bb or bb.
What will be the outcome if a woman who is XXbb produces a child with a man who is XYBb?
a
There is a 75% chance that the child will not become bald.
b
There is a 25% chance that the child will not become bald.
c
There is a 100% chance that the child will become bald.
d
There is a 50% chance that the child will become bald.
choose correct answer
The correct answer is d) There is a 50% chance that the child will become bald.
This is because the woman is XXbb, meaning she does not carry the dominant baldness allele (B). The man is XYBb, meaning he carries one dominant baldness allele (B) and one non-baldness allele (b). There are four possible combinations of alleles that the child can inherit: XB, Xb, YB, or Yb.
Out of these four possibilities, two have at least one dominant allele (XB and YB) and two have only non-baldness alleles (Xb and Yb). Therefore, there is a 50% chance that the child will inherit at least one dominant baldness allele and become bald.