Which offspring is not possible from a mother who is R1R2 and a father who is R1r?

To determine which offspring is not possible from a mother with the genotype R1R2 and a father with the genotype R1r, we need to analyze the potential combinations of alleles they can produce.

The mother possesses two allele forms, R1 and R2, while the father has one copy of R1 and one copy of r. The possible allele contributions from each parent can be depicted as follows:

• The mother can contribute either R1 or R2.

• The father can contribute either R1 or r.

When these contributions are combined, the potential offspring genotypes would be:

1. R1 from the mother and R1 from the father (R1R1).

2. R1 from the mother and r from the father (R1r).

3. R2 from the mother and R1 from the father (R2R1, which is equivalent to R1R2).

4. R2 from the mother and r from the father (R2r).

Now, regarding the Rh gene and the specific genotypes provided, the alleles might also involve the presence of other characteristics (like the D antigen), which needs to be kept in mind.

To assess the choices:

• The combination DcE