Hemizygous
A chromosome in a diploid organism is hemizygous when only one copy is present.
Source:Wikipedia en
Example
For example, this is the case of the gene carried by the chromosome X by males, which has only one chromosome X
A chromosome in a diploid organism is hemizygous when only one copy is present.
For example, this is the case of the gene carried by the chromosome X by males, which has only one chromosome X