Genetics Question

[dentalknight]

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Kaplan Test Question 36

Which of the following is true concerning a sex-linked lethal recessive trait?

a) females cannot carry a gene for it
b) it is dominant in females
c) color blindness is an example
d) it will cause death only in males
e) schizophrenia is an example

 

[PooyaH]

D it is!

 

[socket]

Answer is
d
Males have only one X , the other sex chromosome is a Y, so if the X is a lethal version, even a recesive one is deadly for them.
Women have XX, so the second one masks the lethal recessive gene. Hope you got it...

 

[AndyK]

EDIT: nevermind 🙂

 

[boxdesker]

I don't know if this is implied for you guys or not. But something to add is that, the reason females can't get 2 recessive alleles and die from it is that one of the recessive alleles has to come from the male. Well, if the male has the recessive lethal allele--he'll be dead long before he has a chance to pass it on. Therefore, females can only have at most one of the allele (and there's a 100% chance she got it from her mother). And like Socket said, if you only have one recessive allele, the dominant allele will mask it.