Practice question

Test cross by definition involves crossing F1 or any dominant phenotype individual of uncertain genotype with homozygous recessive parent, which carries two copies of recessive allele and can only produce recessive gametes. This homozygous recessive tester simplifies interpretation because any dominant progeny must have received dominant allele from tested parent, any recessive progeny recessive from both. Crossing with dominant, either or heterozygous parent would obscure analysis, not revealing gamete purity, hence recessive homozygote is standard tester. Cytological correlation with prophase pairing, metaphase alignment and anaphase separation provides visual anchor for memorising genetic laws.