What type of genetic combination is formed from a dihybrid cross producing a 9:3:3:1 ratio?

The formation of a 9:3:3:1 phenotypic ratio from a dihybrid cross is indicative of unlinked genes that assort independently. This specific ratio arises when two traits are being analyzed, and each trait is governed by alleles located on different chromosomes or far enough apart on the same chromosome to assort independently during meiosis.

In a dihybrid cross, such as one examining two traits with two alleles each (for example, AaBb x AaBb), the combinations of alleles can lead to four distinct phenotypes. When the genes are unlinked, they follow Mendel's law of independent assortment, resulting in a mix of alleles that segregate independently. This leads to the characteristic 9:3:3:1 distribution of phenotypes: where 9 exhibit one dominant trait for both genes, 3 exhibit one dominant trait and one recessive for one gene, and so forth.

In contrast, linked genes would not provide this ratio; instead, they tend to assort together more frequently due to their proximity on the same chromosome. Complete linkage would result in even fewer combinations, resulting in phenotypic ratios that reflect only parental types without the expected variety. Incomplete dominance describes a scenario where heterozy