Practice question

A cross between phenotypically dominant individual of unknown genotype and homozygous recessive tester aa produces progeny ratio reflecting gametes from dominant parent. If dominant parent were AA, only A gametes form, so all offspring Aa show dominant phenotype. If dominant parent were heterozygous Aa, meiosis yields equal A and a gametes, producing Aa dominant and aa recessive progeny in 1:1 proportion. Observing 1:1 dominant to recessive therefore diagnoses heterozygosity. This logic excludes homozygous dominant, homozygous recessive, and hemizygous interpretations for autosomal monohybrid trait with complete dominance.