Question

3. Albinism is recessive to normal skin pigmentation. A man who is a carrier for albinism but has normal pigmentation marries an albino woman. What are the genotypic and phenotypic ratios of possible children? 4. Left-handedness is caused by a recessive allele. A left-handed woman whose father and mother are right-handed marries a right-handed man whose mother is left-handed, father is right-handed and sister is left-handed. a. Determine the genotypes of all these people: left-handed woman's right-handed father: left-handed woman's right-handed mother: left-handed woman: right-handed man: right-handed man's left-handed mother: right-handed man's right handed father: right-handed man's left-handed sister: is left-handed mother b. What are the chances that the first child born to this family will be left-handed?

Answer 1

Ans

So albinism is an autosomal recessive disaese that means the affected individual should have a homozygous recessive genotype.

Since the man is carrier his genitype is heterozygous for the disease ,since he has a dominant allele , the recessive allele is not expressed.

4. Here again left handed trait is autosomal revessive .

Let the dominant allele be L and recessive allele be l .

Now since both parents of the womam are right handed but the woman is left handed that means the womans genotype is undoubtedly ll since its an autosomal recessive trait . For the woman to have two recessive alleles each of it should be inherited from both parents which means both parents poesses a recessive allele in the genotype. But since thep are both right handed there must be a dominant allele that supresses the l allele for left handed trait . So the parents are both heterozygous for the trait that is Ll.

Now in the man's case his mother is left handed means autosomal recessive so ll. Then sister is also left handed , again same genotype ll.but since the man is right handed , the father has to posess a dominant allele L. So the father is Ll and not LL ( see the punnet square ) becuase if he is LL and mother is ll all the offsprings will be right handed because of inheriting the dominant L allele from the father .

So the man is also Ll as he inherits L from father and l from mother. And the sister inherits one l from each father and mother.

Attaching image .

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