Albinism is caused by a recessive autosomal allele. A man and woman, both normal

Question

Albinism is caused by a recessive autosomal allele. A man and woman, both normally pigmented, have an albino child together. The mother is now pregnant for a third time and her doctor tells her she is having fraternal twins. What is the probability that both children will have normal pigmentation? Curly hair is caused by a dominant gene in humans. This trait is rare among northern Europeans. If a curly-haired northern European marries a person with straight hair, what proportion of their offspring would be expected to have curly hair, if the curly haired individual was a heterozygote?

Explanation / Answer

1. Alright, so let's call the trait P with P being normally pigmented and is also dominant while we have p having albinism and is recessive. Based on the description of both man and woman having normal pigments but having a kid with albinism says that both parents have to have recessive alleles for the possibility of having an albino kid to exist. So we can assume based on that, that both parents have the alleles Pp so in doing a cross of these two parents, these possibilities open up (I can't do a cross on this writing section so this is the best I can do): PP (25%) Pp (50%) pp (25%) Because as shown through the parents, that having a recessive allele but not two recessive alleles let you have normally pigmented skin (so there's no heteroxygous variation), this means that both children will each have a 75% change of being born with normally pigmented skin. 2. Let's call the allele H with H being curly hair because curly hair is dominant, and h being straight hair because it is recessive. So the parents, one having heteroxygous curly hair (meaning the alleles Hh) and the other having straight hair with the alleles hh, the cross would have a result like this: Hh (50%) - gives curly hair hh (50%) - gives straight hair So that means that 50% of their offspring would expect to have curly hair. Also, you might want to change your username, little depressing, change it to winner12 if you can, good luck :)

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