How do you tell if a disorder is SEX-Linked

If men are affected and never carriers and women are mostly carriers and very rarely affected, it's an X-linked disorder.

the big giveaway that I usually see is if you see a majority of one sex getting the disease, i.e. usually males since they only get one copy of the X chromosome and 1 of Y.

hence they have a higher probability of expressing a sex-linked trait. their mother usually doesn't express the disease since she has 2 copies of X chromosomes, and if its recessive, her dominant copy will prevent her from expressing the disorder.


I dunno about sex-linked dominant traits, i'm sure they're out there but I've never heard anything about it.

sorry if this doesn't make sense, i'm pretty tired lol


edit: just saw foghorn's post...great summary of the possibilities

how can you tell if a disorder is sex-linked

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Prominent calluses on the hands and "chafing of the willy".

Foghorn said:

For sex-linked
Assuming father carries normal/wild type sex chromosomes

X dominant with XX mom (she has the disorder) ----> all progeny get it (the disorder)

X dominant with Xx mom (she has the disorder) ------> half of all progeny get it

x recessive with Xx mom ------>female progeny are normal, half of males get it

x recessive with xx mom-------->female progeny are normal, all of males get it


You can make up other scenarios where the father carries the abnormal chromosome that's dominant/recessive. And also do F1, F2 etc generations.

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Well said.

DropkickMurphy said:

Prominent calluses on the hands and "chafing of the willy".

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Well said.

Just to elaborate, there are two more cases (which don't assume that the father is normal!):

X dominant with X father (he has the disorder) ----> Daughters get it (the disorder)

X recessive with xx father (he has the disorder) and Xx mother (she seems normal) ----> half female progeny have it, half males have it (the disorder)