Genetics Question : Albinos

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Eflex tha Vybe Scientist

Registered Senior Member
Behold a pale human.

I have a question for all the geneticists.

I just completed a trip to Nigeria ( a truly beautiful place)
While I was travelling the country, I noticed many albinos amoungst the general population.
(not really a big deal, but I got to thinking)

Since the genome indicates that all humans have the genes to manufacture melanin,
Why dont we ever see a dark skinned (highly pigmented) child born to a Swedish couple?

I've racking my brain for the the evolutionary answer, but since the mechanism for two Nigerians having an albino child is purely chance, why doesnt chance ever have a German couple give birth to a darker skinned child?
 
maybe we don't have an answer. I didn't. I never heard of the exception. And I can't figure out why. It is probably something simple, but what?
 
hi,
the apparatus that generates pigmentation is rather complex and defects can lead to incomplete or absent pigmentation (albino) (overall or even restricted to the eyes (as far as i could judge from this paper i skimmed) this means that already a simple mutation can lead to albinism (spelling?) : loss of function.
the gain of function mutationfor a pale skinned couple to have a more strongly pigmented child would be much much more rare.

apart from that: apparently a number of diseases/some chemicals/drugs (melanomas!)may cause localized hyperpigmentation, but these wouldnt appear normally, dark-skinned (i think)


hope this helps, Bart

ref:
Human pigmentation genetics: the difference is only skin deep.
Bioessays. 1998 Sep;20(9):712-21. Review.
:)
 
thanks for the replies.

I agree that skin pigmentation doesnt make humans a different race from other humans. Homo Sapiens is what we all are.

When you say that a 'paler' couple having a darker child is even more rare.
Has there ever been a documented case of this occurring?
 
It's simple. Albinism is not caused by genes from parents..it is due to a enzyme defficency. Germans couldn't have a dark skinned child because their Genes won't allow it...but Nigerians can have a albino child because for one of many reasons that child could have the enzyme defiency.
 
Albinism is genetic, resulting in an enzyme deficiency. It can be inherited from the parents. I have no answer for the original question though. However, bmengels' explanation sounds good to me.
 
Yeah albinism is genetic....a mutation causing the enzyme deficiency is passed on to the offspring. There is still a chance of a spontaneaous mutation occuring so that a child has the enzyme deficiency even though the parents didn't.

Races that naturally have lighter skin don't necassarily have albinism, they are just adapted to their envirnment. Sure there are still albinos; but these occur for the same reasons as the nigerians have albinism. There isn't such a simple mutation that can cause a naturally light skinned person to be dark and is why we don't ever see it.
 
Originally posted by koolmodee
Yeah albinism is genetic....a mutation causing the enzyme deficiency is passed on to the offspring. There is still a chance of a spontaneaous mutation occuring so that a child has the enzyme deficiency even though the parents didn't.

Races that naturally have lighter skin don't necassarily have albinism, they are just adapted to their envirnment. Sure there are still albinos; but these occur for the same reasons as the nigerians have albinism. There isn't such a simple mutation that can cause a naturally light skinned person to be dark and is why we don't ever see it.
Click to expand...

thanks for the replies everybody!!!

kool name, koolmodee!
how ya like me now?

anyway,
Since albinism is genetic, the result is a mutation that causes enzyme deficiency. OK got it.
Since there is a chance that albinism can be caused by a spontaneous mutation , as a result of environment, gamma rays, ultraviolet radiation etc...

Is there a chance that a sponaneous mutation can occur in a not so simple way that could cause a naturally light skinned person to produce a darker child?

or is this just impossible?
 
I don't remember how many genes are involved in skin pigmentation. But in places like Mexico, where races are quite mixed, a more or less dark skinned couple can have a fair skinned child if there are fair skinned ancestors on both sides of the family.
 
Originally posted by Eflex tha Vybe Scientist
kool name, koolmodee!
how ya like me now?
Click to expand...
Yeah you're alright ;)
anyway,
Since albinism is genetic, the result is a mutation that causes enzyme deficiency. OK got it.
Since there is a chance that albinism can be caused by a spontaneous mutation , as a result of environment, gamma rays, ultraviolet radiation etc...

Is there a chance that a sponaneous mutation can occur in a not so simple way that could cause a naturally light skinned person to produce a darker child?

or is this just impossible?
Click to expand...
I don't think so. Albinism is a deficiencey in the genes; having dark skin isn't ...so I can't really see how it would just change like that.
 
Because skin pigmentation is determined by several genes it would be very unlikely for all of these to spontaniosly mutate to create a dark skinned child from light parents. But I'm sure there are cases of only one of the genes mutating, this would only make the skin color slightly darker than the parents though, probably not noticeable enough to matter. I've seen plenty of kids that were a little bit darker than thier parents,or lighter for that matter.
 
Albinism is a relatively rare trait that can only be caused when the two recessive albino alleles form in one or more of the many genes responsible for hair color. The resulting lack of the enyzme that produces hair pigmentation results in the loss of color.
 
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