Why am I weak in color, but my parents, grandparents and grandparents are normal? Why! ! ! !

The sex chromosome of a man is xy, and that of a woman is xx. Color weakness is a sex-linked recessive inheritance, and the genetic gene exists on the X chromosome of the sex chromosome.

Let's talk about the performance of weak color first. The weak color gene carried by the boy is dominant, that is, if the boy is weak in color, he will have symptoms, such as being unable to tell red from green. The weak color gene carried by the girl is recessive (unless the girl gets an X with the weak color gene from her parents), that is, if the girl is weak in color, she has no symptoms and normal color discrimination ability, but she has a genetic gene.

Grandpa is weak in color, and his daughter has an X chromosome with his father's weak gene, so this daughter 100% inherited his father's weak gene. The boys she gave birth to have a 50% chance to inherit the weak color gene, and the girls she gave birth to have a 50% chance to inherit the recessive weak color gene. Because both boys and girls will get one of the mother's two X's (if this daughter's two X's have weak color genes, then her daughter and son have 100% with weak color genes).

In another case, the boy's grandfather is pale. Even if the boy inherits the weak color, if the boy's child is a boy in the future, the weak color gene will be cut off and will not be inherited, because he gave his son a normal Y (of course, this premise is that the father of the boy's wife must not be weak color, otherwise it will be like the "grandpa problem" in front. ) If you are a girl, start cycling this 50% game.