Question

Which of the following is a key distinguishing feature of co-dominance when comparing genotypic and phenotypic ratios?

Options

• The genotypic and phenotypic ratios are identical (1:2:1)

• The phenotypic ratio is always 9:3:3:1

• The phenotypic ratio is always 3:1 regardless of the genotypic ratio

• The genotypic ratio is always hidden and cannot be determined from phenotypes

Answer 1

In co-dominance, the genotypic and phenotypic ratios are identical. This occurs because each different genotype (RR, RW, WW) produces a distinctly different phenotype (Red, Roan, White). This contrasts with complete dominance where a 3:1 phenotypic ratio results from a 1:2:1 genotypic ratio, and both phenotypes cannot always be distinguished from the genotype alone.