Library · Genetics
X-linked inheritance
Make it clearer
There are two sex chromosomes, and one of them is the X. When a disease is called X-linked, it means it is caused by variants, or changes, in genes that live on that X chromosome.
And that is where an asymmetry shows up that explains almost everything. In males, who have a single X chromosome, a change in the only copy of the gene in each cell is enough to cause the condition: there is no second copy to fall back on. It is the difference between leaving home with a single key and leaving with two: if that key breaks, there is no spare in your pocket. In females, who have two X chromosomes, one altered copy usually causes milder health problems than in affected males, and sometimes causes no signs or symptoms at all. There is also a rule of transmission that helps you recognize this pattern in a family: a father cannot pass X-linked traits to his sons.
In brief
X-linked disorders are caused by variants in genes on the X chromosome, one of the two sex chromosomes in each cell.
In males, who have a single X chromosome, a change in the only copy of the gene is enough to cause the condition.
In females, who have two X chromosomes, one altered copy usually causes milder problems than in affected males, or no signs or symptoms at all.
One hallmark is that a father cannot pass X-linked traits to his sons.
Sources (1)
- MedlinePlus GeneticsWhat are the different ways a genetic condition can be inherited?
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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