Mutations in the three genes are all autosomal recessive and the three genes are unlinked.Two different true breeding mice have been isolated that do not make any antigen (neither 1 or 2). A Cross of these two different mice produce F1 that make both antigens.What are the genotypes of the two parents?

Let's call gene 1, 2, 3 as gene X, Y, Z respectively.

Parent 1 = xxYYZZ

Parent 2 = XXyyzz

(or vice versa)

Explanation:

Since all of the three mutations are said to be recessive and un-linked. According to the question statement, neither parents have the ability to make any antigen. When these two genotypes will be crossed, a genotype XxYyZz will be obtained. This one will be capable of producing antigen.

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