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.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

we would need to see the picture to answer it