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Dear student,

If disorder is X-linked recessive like colour blindness, then there would be smaller proportion of females suffering ( as
XCXC condition is required in females to suffer,  which is very rare ) while there would be higher male percentage suffering from it as they do not have corresponding X allele. 

Males can never be carrier of colour blindness. Since males have only one X chromosome, the allelic counterpart is absent so the trait is always expressed in males and hence they cannot be carriers. Females can be carrier as well as colour blind (sufferer). As we know, females have XX chromosome so, if gene on one of the chromosome is affected , it will be compensated by the other and in this condition females become carrier.

Another characteristic of X-linked disease like colour blindness is that X-linked traits  cannot pass from fathers to their sons. It shows crisscross inheritance because in this disorder father passes gene for disorder to carrier daughter who then transmit it son.

Here is a given a pedigree analysis for colour blindness.


So, if the father is color blind then this trait will not get pass onto the son, therefore son will be normal XY. The trait will get passed from a color blind father to his daughter and she will be a carrier in this case which can be denoted by XCX. The cross between normal male XY and a carrier female XCX will give XCX, XX, XCY and XY. Therefore, chances of their daughter to be carrier for this trait is 25%.


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