X-linked recessive trait/disorder?

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What is an x linked recessive trait and how is it passed on?

X-linked recessive trait/disorder?
Between two alleles for one gene sometimes one can over ride the other masking it. This is called dominance.


Because the reproductive chromosomes are not identical inclusion of a recessive is different than in autosomal chromosomes.


If the x chromosome carries a recessive gene it will be expressed in a male despite being recessive because the y chromosome does not carry the dominant. However this same recessive bearing x chromosome in a female could be masked by a dominant bearing chromosome.


Color blindness in humans is x linked.


http://www.lpch.org/DiseaseHealthInfo/He...
Reply:X-Linked means that the gene of interest is found on the X chromosome (recall that females have 2 X chromosomes while males have 1 X and 1 Y). Recessive means that an individual must be homozygous (have the exact same gene for both copies) for the recessive gene for its phenotype to be expressed. The phenotype is the observable trait. So, X linked recessive traits are passed on to children when they inherit that X chromosome.


However, the mother always provides an X (1 in 2 possible ones), but what the father gives determines the sex of the child. If the father gives an X it is a girl, but if he gives a Y it is a boy. So, if the mother passes on an X with the recessive gene, the trait will definetly show up in boys but may or may not show up in girl depending on whether the father has a recessive gene on his X chromosome.

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