If a female is a carrier for colour blindness, marries a male which is normal, then in the offsprings this disease may be seen in ?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) - 50% sons diseased and 50% daughters (carrier).
- Color blindness is a sex-linked recessive disorder, meaning the gene responsible is located on the X chromosome.
- A female carrier has one normal X chromosome and one X chromosome with the color blindness gene (XCX).
- A normal male has one X chromosome and one Y chromosome (XY).
When a carrier female (XCX) marries a normal male (XY), the possible combinations for their children are:
- For sons:
- Sons inherit the Y chromosome from their father and one X chromosome from their mother.
- There’s a 50% chance a son will inherit the XC (color-blind gene) and become color-blind (XCY).
- There’s a 50% chance a son will inherit the normal X and be normal (XY).
- For daughters:
- Daughters inherit one X chromosome from each parent.
- There’s a 50% chance a daughter will inherit the normal X from both parents, making her normal (XX).
- There’s a 50% chance a daughter will inherit the XC from the mother and the normal X from the father, making her a carrier (XCX), but not color-blind.
Therefore, 50% of the sons will be diseased, and 50% of the daughters will be carriers.