Definition of Hemizygous

Hemizygous is a male mammal which has a single copy of an X-linked gene present in it. It can also be defined in the following way: In a diploid organism, a chromosome is said to be hemizygous when only one copy is present. This is observed in a heterogametic sex cell when the gene is located on the germ line chromosome or when one copy of a gene is deleted.


The organisms such as humans in which the male is heterogametic, all the X-linked genes are hemizygous in the autosomes as they constitute only one X chromosome and some of the same genes are also present on the Y chromosome.


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