Correct Response: B. Since colorblindness is sex-linked and recessive, a female must receive two alleles for the trait to be expressed, one from the X-chromosome of the biological mother, and one from the X-chromosome of the biological father (B). A sex-linked trait is carried on the X-chromosome. Since a male has only one X-chromosome, and this father passed down the trait to his daughter, his X- chromosome must carry the trait; therefore, he is colorblind, so (C) cannot be true. A female has two X- chromosomes, of which only one is passed on to her child. Since the daughter received an X- chromosome that carried the trait from her mother, the mother could have been colorblind (A), or a heterozygote carrier (D), but it cannot be determined from the information given which genotype is true in this case
