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Why is it that human females usually have dominant traits and human males usually have recessive traits?
Question Date: 2013-02-19
Answer 1:

That's an interesting question. Human males and females typically display equal amounts of dominant and recessive traits. We get 2 copies of each gene on each autosomal (non-sex specific) chromosome: one set of copies from our father and one from our mother.

A recessive gene causes a phenotype (an expressed characteristic) when an individual is homozygous for that gene (has 2 copies). A dominant trait will be expressed with only one copy of the gene (heterozygous). Therefore, whether a person is recessive or dominant for a given trait will depend on their parents' genetic makeup. Traits can also be semi-dominant (the genetics that determines our blood types are an example of this).

There are certain traits and diseases that are linked to genes that are on the X chromosome only (females are XX, males XY). So if a male gets one of these genes on his X chromosome (from his mother), he will express the trait, whether it is dominant or recessive (because he has only 1 X chromosome). If a man has an X- linked dominant trait, his daughters will express that gene (they get his X chromosome; if it is recessive, they will be a carrier of that gene). In contrast, if a mother has an X-linked dominant trait, her daughter's have a 50% chance of receiving that trait.

I hope this answers your question!

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