A child has colorblindness. Which genotype-phenotype combination is NOT possible in the child’s parents?
--The father carries one allele and has color blindness.
--The father does not carry the allele and does not have color blindness.
--The mother carries one allele but does not have colorblindness.
--The mother carries two alleles and has colorblindness.
--The father carries one allele and but does not have colorblindness
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--The father does not carry the allele and does not have color blindness.
Since colorblindness is a recessive trait, both parents must at least have the allele if not the phenotype trait of colorblindness.
A child has colorblindness. Which genotype-phenotype combination is NOT possible in the child’s parents?
D) Is not possible. As the previous answerer mentioned, this is because color blindness is sex-linked, meaning it's carried on the X chromosome. Because men have XY chromosomes and women have XX chromosomes, men only get one copy of the gene involved in color blindness. As such, if men have just one copy of the X-linked gene for color blindness, they have no second copy to back up its function. A woman, on the other hand, has two X-chromosomes, so if one carries the defective gene, there is a second "backup" copy. For a woman to get color blindness, both copies of the woman's gene must be defective. Hope this helps!