Use the pedigree chart to explain why the yellow allele is recessive - HSC - SSCE Biology - Question 26 - 2020 - Paper 1

The yellow allele is recessive as seen in the pedigree chart. Both parents (shown as orange) have the genotype that allows for the expression of yellow colour but show an orange phenotype. The presence of yellow offspring indicates that both parents must carry the yellow allele in a recessive form.

Since both parents are orange, they carry a genotype of Aa (where A = orange and a = yellow). When they produce offspring, it is possible for both to pass on the recessive yellow allele (a), resulting in offspring that express the yellow phenotype. Thus, the yellow allele remains masked in the parental generation but can express in the offspring generation if both parents pass it on.