Question: We have discussed how recessive phenotypes are more likely to be
expressed in males if the corres…
We have discussed how recessive phenotypes are more likely to be
expressed in males if the corresponding gene is found on the
X-chromosome. For example, one-type of colorblindness is caused by
a recessive X linked allele, and this trait is much more common
inmales than females. But we have also discussed how, in placental
mammals, one copy of each X chromosome is randomly silenced in
female cells (X inactivation). This raisessomewhat of a paradox.
Why don’t half of heterozygous females exhibit colorblindness just
like hemizygous males that carry the recessive allele?
Based on your under standing of Xinactivation in placental
mammals, provide an explanation for why heterozygous females
generally do not exhibit colorblindness despite the random
silencing of one X chromosome.
b.How would your answer change if we were talking about a
marsupial mammal (inwhich the paternally inherited copy of the X
chromosome is inactivated in every cell)? Would you expect half of
heterozygous females in a marsupial species toexhibit color
blindness? Why or why not?