Certain forms of human color blindness are inherited as X-linked recessive traits. Hemizygous males are color blind, but heterozygous females are not. However, heterozygous females sometimes have partial color blindness.

A. Discuss why heterozygous females may have partial color blindness.

B. Doctors identified an unusual case in which a heterozygous female was color blind in her right eye but had normal color vision in her left eye. Explain how this might have occurred.