Question

Red-green color blindness is an x-linked recessive condition in humans. a man with normal vision had 8 children with a women that had normal vision; 2 sons were color blind, 2 sons had normal vision, all four daughters had normal vision. what is the expected genotype of the mother? xby xbxb xbxb xbxb

Answer 1

1) recessive allele is b
    dominant allele is B
When an X chromosome contains the dominant allele,is written as: $X^B$
When an X chromosome contains the recessive allele, is written as:$X^b$

2) the genotype of the woman is $X^BX^b$ She is not color-blind but she is a carrier of red-green color blindness, who passed the allele to their sons.
Woman,  have two X chromosomes.  If she is not colorblind is because there is the dominant allele making her see normally. But, she is a carrier, so while one X chromosomes has the dominant allele, the other has the recessive (making her carry the disease).