A woman is a carrier for red-green color blindness, a sex-linked trait. Her husband is normal (not color-blind) for this trait. What are the chances that their newborn daughter will be red-green color-blind?

• A. 25%
• B. 50%
• C. 75%
• D. 100%
• E. 0%

Answer: (E)

Verified step by step guidance

1. Understand that red-green color blindness is a sex-linked trait, specifically linked to the X chromosome. This means that the gene responsible for this condition is located on the X chromosome.
2. Recognize that a woman who is a carrier for red-green color blindness has one normal X chromosome and one X chromosome with the color blindness allele. Her genotype can be represented as X^CX^c, where X^C is the normal allele and X^c is the allele for color blindness.
3. The husband is normal for this trait, meaning he has a normal X chromosome and a Y chromosome. His genotype is X^CY.
4. When they have a daughter, she will inherit one X chromosome from each parent. The possible combinations for the daughter are: X^CX^C (normal) or X^CX^c (carrier).
5. Since the daughter inherits one X chromosome from her father, which is normal (X^C), she cannot be color-blind because she would need two X chromosomes with the color blindness allele (X^cX^c) to express the trait. Therefore, the chance of their daughter being red-green color-blind is 0%.