When a color-blind male marries a normal female, what will be the chances of colorblindness in his grandsons, if his daughter is married to a normal male?

Explanation

The chances of colorblindness in the grandsons of a color-blind male, when his daughter is married to a normal male, depend on the specific inheritance pattern of color blindness. Color blindness is a sex-linked trait that is predominantly inherited on the X chromosome. The gene responsible for color vision is located on the X chromosome, and males have one X chromosome (inherited from the mother) and one Y chromosome, while females have two X chromosomes (one inherited from each parent). Assuming the color-blind male is affected by an X-linked recessive form of color blindness, the following scenarios are possible: If the daughter inherits the normal X chromosome from her color-blind father: In this case, the daughter will be a carrier of the color blindness gene, but she will not have color blindness herself. She will pass on the color blindness gene to her offspring with a 50% chance of passing it to each child. If the daughter inherits the color-blind X chromosome from her color-blind father: In this case, the daughter will be color-blind and has inherited the color-blindness gene on her X chromosome. She will pass on the color blindness gene to all of her sons, who will be affected by color blindness. If the daughter marries a normal male, who does not carry the color blindness gene, the chances of color blindness in their grandsons will depend on whether the daughter is a carrier or affected by color blindness herself. If the daughter is a carrier: Sons: Each son will have a 50% chance of inheriting the color blindness gene from his mother and being affected by color blindness. Daughters: Each daughter will have a 50% chance of inheriting the color blindness gene from her mother and becoming a carrier, but she will not have color blindness herself. If the daughter is affected by color blindness: Sons: Each son will inherit the color blindness gene from his mother and be affected by color blindness. Daughters: Each daughter will inherit one color-blind X chromosome from her mother and one normal X chromosome from her father, making her a carrier of color blindness. it's important to note that this explanation assumes a simplified scenario based on classic Mendelian genetics and a single gene responsible for color blindness. In reality, color blindness can be caused by different genetic mutations and may exhibit variations in inheritance patterns. Genetic counseling or consulting a healthcare professional with knowledge of genetics can provide a more accurate assessment of individual cases. The official NTS key marks C as the correct answer. The crosses are as follows: