sex linked traits
A particularly important category of genetics has to do with the X and Y sex chromosomes. These X and Y chromosomes are unique. When a trait is carried on the Y chromosomes, that makes it impossible for a female to have that trait. When a trait is on the X chromosome, both men an women can inherit it. However, it is more common for a man to inherit a recessive gene carried on the X chromosome because men only have one X, meaning there would be no chance of a dominant allele overriding a recessive allele should they inherit one.
Let's use the punnett square to the right as an example. On the top of the punnett square is the mothers genotype, which shows she is a carrier of a recessive sex-linked disease. The father's genotype shows that he does not have the disease. The two offspring on the top are female. There is a 0% of these two parents having a daughter with the disease, and a 50% chance of them having a daughter who is a carrier. The bottom two offspring are the males. As you can see, there is no allele on the Y chromosome image source: http://www.biologycorner.com
because it is an X-linked disease.
There is a 50% chance that their male child will have the disease. Because males only have the one X, they either inherit the disease or they don't. There is no such thing as a male carrier of an X-linked trait.
Let's use the punnett square to the right as an example. On the top of the punnett square is the mothers genotype, which shows she is a carrier of a recessive sex-linked disease. The father's genotype shows that he does not have the disease. The two offspring on the top are female. There is a 0% of these two parents having a daughter with the disease, and a 50% chance of them having a daughter who is a carrier. The bottom two offspring are the males. As you can see, there is no allele on the Y chromosome image source: http://www.biologycorner.com
because it is an X-linked disease.
There is a 50% chance that their male child will have the disease. Because males only have the one X, they either inherit the disease or they don't. There is no such thing as a male carrier of an X-linked trait.