What is a "Barr body?" Explain how women heterozygous for traits coded by genes on the sex chromosomes express the dominant allele even if many of the dominant alleles for the trait have been condensed into Barr bodies.
In females, only one of the X chromosomes is active in somatic cells. The other condenses into a small dark body called a Barr body. The genes on the Barr body are inactive. In women who are heterozygous for traits coded by genes on the sex chromosomes, half of the dominant alleles and half of the recessive alleles are condensed into inactive Barr bodies, but, as long as some dominant alleles function in some cells, the recessive alleles are not expressed.
