In guinea pigs, the allele for black hair (B) is dominant to the allele for brown hair (b). The allele for short hair (S) is dominant to the allele for long hair (s). The genes for hair color and hair length are located on different chromosomes. Guinea pigs with black, short hair (BbSs) are crossed with guinea pigs with brown, long hair (bbss). Some offspring have black, short hair or brown, long hair like the parents. Additionally, some offspring have black, long hair or brown, short hair. Which of the following explains the different phenotypes in the offspring?
1) The expression of the alleles for hair color is influenced by the alleles for hair length.
2) The alleles for hair color and hair length assort independently during gamete formation.
3) The alleles for hair color and hair length mutate during the first cell divisions of the offspring.
4) The interaction between the alleles for hair color and hair length is incomplete dominance