Heyo,
Iv been wondering About the molecular inheritance and I stumbled upon the term Barr’s body. From my understanding, when a cell has more than one X chromosome (women, Klip. syndrome, superwomen genotype), the extra X chromosomes get condenzated and are located on the side of the nucleus and get inactivated.
So, to my question – is There even something such as dominantly and recessive gonosomal disease since There isnt any counter part to the gen on X chromozome? (Im only taking the genes outside of pseudoautosomal zone into consideration).
Thanks in advance ^ ^
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I think you’re talking about X-linked conditions.
In each cell with more that one X chromosome (for the rest of this we’re just going to a work with the number 2 for simplicity) which X becomes that Barr body is random. So half the cells have the same X working and the other one quiet.
The majority of X-linked conditions are X-linked recessive. Meaning that people with two X chromosomes who have one defective copy almost always the other copy functioning (major bad luck if both are non-functioning). This is enough to give normal function. This with only on X don’t have a back up, so a non-functioning gene will lead to whatever is involved (e.g red-green colourblindness).
There are a few conditions where one defective gene copy is enough to cause the condition, X-linked dominant conditions. There are relatively few of these conditions. In some of the conditions, they only affect females because males don’t survive (either miscarriage or still birth). In others, the males are usually more severely affected than females, as the females have an spare functioning gene copy, but it’s not enough to completely compensate for the defective one.
An example of an X-linked dominant condition is Incontentia pigmentosa. The vast majority of patients are females are very few males survive birth. An example where there are males affected is Fragile-X syndrome. Females with the affected gene may have no symptoms, but around half to two-thirds will have features, but less severe than the males (eg males with fragile-x have moderate intellectual disability, while affected females have a milder intellectually disability).
I hope I’ve understood your question correctly and answered it. Let me know if I’ve completely misunderstood and I’ll try to answer what you mean
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