Final answer:
When a male who is normal for color vision marries a female who is a carrier for color blindness, there is a 50% chance that they will produce a son who is color blind.
Step-by-step explanation:
When a male who is normal for color vision (not color blind) marries a female who is a carrier for color blindness, there is a chance that they could produce a son who is color blind. Color blindness is an X-linked recessive trait, which means that it is carried on the X chromosome. Boys have only one X chromosome, so if that chromosome carries the gene for color blindness, they will be color blind. Girls have two X chromosomes, so even if one X chromosome carries the colorblind gene, the other X chromosome with a normal gene for color vision will mask the recessive colorblind gene. Therefore, females with one colorblindness allele and one normal allele are carriers and do not express the trait.
Based on this information, the probability of the couple producing a colorblind son can be determined using a Punnett square. Since the female is a carrier (heterozygous), she can pass on either the normal allele or the colorblind allele to her offspring. The male will always pass on his normal allele since he does not have the colorblind allele. The Punnett square for this cross would show that there is a 50% chance of producing a son who is color blind.