Question

What is hemizygous?

Answer 1

Hint: The condition where both the two copies of genes or chromosomes are genetically similar having the same genetic sequence. It can also be said that the condition in which one allele is missing and the other alleles are similar.

Complete answer:
Biological sex is decided by a pair of sex chromosomes: for which XY in males and XX in females, in humans and other mammals.
The condition in which only DNA sequence or a single copy of the gene is found in the diploid cells is called hemizygous condition. Males consist of two sex chromosomes X and Y chromosomes and are thus said to be hemizygous for several genes present on the sex chromosomes.
Example: It is often observed that the males have either orange or black fur, though both the males and the females have the ability to produce either black or orange fur, the gene for this is present on the X chromosome. Since females have both X chromosomes, they display both the colors while males have only one X chromosome so they may be either orange or black.

Additional information:
A chromosome is said to be hemizygous when only a single copy of it is present during a diploid condition in an organism and the organisms in which this condition is found are called hemizygotes. Hemizygosity occurs when one of the gene copies is either deleted or missing or is in the heterogametic condition found on a chromosome. Hemizygosity differs from must not be mistaken for haploinsufficiency although they look similar and are responsible for maintaining the phenotype. X-linked genes are mostly hemizygous in the case of males as they are heterogametic in nature having one X chromosome which is equivalent to one Y chromosome.

Note:
The application of hemizygosity can be observed in the case of transgenic mice that are produced by the process of microinjection of an undeveloped organism's pronucleus having only one copy of any locus. To maintain homozygosity in transgenic individuals they are bred with homozygous species and thus maintains the genotype of every individual.