Write a paragraph explaining why a color-blind man who has three daughters and one son with normal color vision might have two grandsons who are color-blind. Use the terms in the vocabulary box in your answer. Underline each term.
Mother must be homozygous for normal vision, which means the daughters would have been carriers (heterozygous), allowing them to pass the recessive colorblind genes to their sons. (Remember that colorblindness is X-linked.)
I'll let you rephrase the information to include the above terms.
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A color-blind man who has three daughters and one son with normal color vision might have two grandsons who are color-blind due to the presence of a recessive allele for color blindness. Color blindness is caused by a recessive genotype, meaning that an individual must inherit two copies of the color-blindness allele (one from each parent) in order to have the color-blind phenotype. In this case, the color-blind man likely passed on his recessive color-blindness allele to his son, who is a carrier of the trait. If the son then goes on to have children with a partner who is either a carrier or is color-blind themselves, there is a chance that their offspring could inherit the recessive color-blindness allele and exhibit the color-blind phenotype. This can result in the occurrence of two grandsons who are color-blind in the next generation.
