MCAT: All Sex Linked--> X-linked recessive

[axp107]

For the MCAT atleast..

are all sex linked disorders X-linked and recessive? It seems like it.

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[majik1213]

For the MCAT at least.. are all sex linked disorders X-linked and recessive? It seems like it.

They aren't all recessive, for consider Coffin-Lowry syndrome, familial rickets, incontinentia pigmenti, or hereditary nephritis, which are four examples of sex-linked dominant diseases.

 

[axp107]

x-linked isn't a synonym for sex linked.. it means disorders of the X chromosome

there are also y-linked disorders.. but there are verrrrry few ones

I'm asking this question b/c from all the MCAT practice I've been doing and pedigrees and everything, we've only had to deal with "X-linked" recessive disorders and autosomal disorders.

 

[majik1213]

yeah, I think I never came across an x-link dominant pedigree .. now watch that be passages VI and VII on BS this friday. Ho hum.

 

[axp107]

oh really..

it's not really that different right.. except

For recessive diseases if you have: XaY, the male has the disease


But if its dominant.. then if you have XaY... the male is a carrier right and doesn't have the disease right?

where a=recessive allele and A = dominant

 

[ilovelucy]

oh really..

it's not really that different right.. except

For recessive diseases if you have: XaY, the male has the disease


But if its dominant.. then if you have XaY... the male is a carrier right and doesn't have the disease right?

where a=recessive allele and A = dominant

Actually, if it is a disease carried on the X chromosome and the mother passes it, the male will ALWAYS get it even if it is dominant or recessive. There is not another X chromosome to "block" the X chromosome so to speak if it was recessive, so the trait will always show in a male (color blindness for example). A female would not get it if it was a dominant disease unless her father had the disease (and the father would ALWAYS pass her the x chromosome) and her mother had at least 1 affected chromosome.

Hope this helps.

 

[majik1213]

haha I just read the title to this thread, "All Sex Linked--> X-linked recessive" as "Anal Sex Linked--> X-linked recessive." wow definitely time to stop studying, ya know?

 

[mrmilad]

If a disease was X linked dominant, then all female and male offsprings would be affected. Pedigree would look like a lit up christmas tree.

 

[zackscoot]

If a disease was X linked dominant, then all female and male offsprings would be affected. Pedigree would look like a lit up christmas tree.

If a disease is X-linked dominant, it will act like an autosomal dominant disease. and it will be very hard to distinguish the two. So which is why MCAT are less likely to ask you this question unless they tell u that the disease itself is X-linked dominant.