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Analyze the pedigree given here, answering the questions that follow. a. What is

ID: 101641 • Letter: A

Question

Analyze the pedigree given here, answering the questions that follow. a. What is the most likely mode of inheritance of this trait: autosomal or X-linked? Give and explain at least two reasons to support your answer, referring to specific examples in the pedigree. b. What is the most likely mode of inheritance of this trait: dominant or recessive? Give a reason to support your answer, referring to a specific example in the pedigree. c. Providing a legend for your symbols, give the genotypes of these six individuals I-2, II-2, II-4, III-2, III-6, IV-11.

Explanation / Answer

a.Mode of inheritance is X linked. In X linked inheritance a mutation in a gene on the X chromosome causes the phenotype to be expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation,

b.X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation.

c I-2.Normal male-XY

II-2 Normal female -XX

II-4 Normal male- XY

III -2 Affected male XY

III-6 Normal male- XY

IV -11- Carrier female - XX