Skewed X-inactivation
Encyclopedia
The random X-inactivation
which occurs early in a developing female can result in skewed or non-random X-inactivation for a patch, tissue or organ.
During the process of X-inactivation
one of the female's two X chromosome is inactivated. For the whole animal this is random but for an individual cell or tissue it is not. For example, fur patches of a tortoiseshell cat
are orange or black due to inactivation of one X chromosome in the patch.
This becomes important in medicine when a carrier
female of an X-linked recessive
condition 'randomly' inactivates the chromosome containing the unaffected gene. This can lead to mild symptoms of the disease. An example is in about 10% of carrier mothers of hemophilic boys.
X-inactivation
X-inactivation is a process by which one of the two copies of the X chromosome present in female mammals is inactivated. The inactive X chromosome is silenced by packaging into transcriptionally inactive heterochromatin...
which occurs early in a developing female can result in skewed or non-random X-inactivation for a patch, tissue or organ.
During the process of X-inactivation
X-inactivation
X-inactivation is a process by which one of the two copies of the X chromosome present in female mammals is inactivated. The inactive X chromosome is silenced by packaging into transcriptionally inactive heterochromatin...
one of the female's two X chromosome is inactivated. For the whole animal this is random but for an individual cell or tissue it is not. For example, fur patches of a tortoiseshell cat
Tortoiseshell cat
Tortoiseshell describes a coat coloring found mostly in female cats. Cats of this color are mottled, with patches of orange or cream and chocolate, black or blue. They are sometimes called torties...
are orange or black due to inactivation of one X chromosome in the patch.
This becomes important in medicine when a carrier
Genetic carrier
A genetic carrier , is a person or other organism that has inherited a genetic trait or mutation, but who does not display that trait or show symptoms of the disease. They are, however, able to pass the gene onto their offspring, who may then express the gene...
female of an X-linked recessive
X-linked recessive
X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males and in females who are homozygous for the gene mutation X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on...
condition 'randomly' inactivates the chromosome containing the unaffected gene. This can lead to mild symptoms of the disease. An example is in about 10% of carrier mothers of hemophilic boys.