Which of the children will be color blind if their mother is a carrier of the gene for color blindness and their father is color blind?
As you know, the gene that causes the development of color blindness is inherited in the X chromosome and is recessive in relation to the gene for normal vision.
Let’s designate the chromosome that includes the gene for color discrimination (color blindness) pathology as Xd, then the chromosome with the gene that causes the normal color discrimination will be XD.
A man with color blindness – Xd Y. He produces two types of spermatozoa – Xd and Y. He transmits a chromosome with a color blindness gene – Xd to his daughters, and a Y chromosome to his sons.
The mother carrier has the XDXd genotype and produces XD and Xd eggs.
The offspring of this couple includes the following options:
heterozygous girls carrying the gene for color blindness (XDXd) – 25%;
healthy boys (XD Y) – 25%.
boys with color blindness (XdY) – 25%;
girls with color blindness (XdXd) – 25%.
Answer: both boys and girls can be color blind in this family. The probability of having a boy with color blindness is 25%, a girl with color blindness – 25%.
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