In a species of flowering plant, the synthesis of a red anthocyanin pigment requires the cooperative action of two independent enzymes encoded by genes A A\,A and BBB. A plant must possess at least one dominant allele of both genes (A A\,A and BBB) to produce red flowers; all other genotypes result in white flowers.
How is a plant with the genotype Aabb Aabb\,Aabb described genetically, and what is its flower phenotype?
Heterozygous at the first locus and homozygous recessive at the second locus; red flowers.
Heterozygous at the first locus and homozygous recessive at the second locus; white flowers.
Homozygous dominant at the first locus and heterozygous at the second locus; white flowers.
Homozygous recessive at the first locus and heterozygous at the second locus; white flowers.
97 exam-style questions on OCR GCSE Biology 5.1 Inheritance, covering 5.1.1 The genome, 5.1.2 Environment and phenotype, 5.1.3 Variants and mutations, 5.1.4 How genetic variants influence phenotype, 5.1.5 Asexual and sexual reproduction, 5.1.6 Haploid and diploid, 5.1.7 Meiotic cell division, 5.1.8 Single gene inheritance, 5.1.9 Predicting single gene crosses, 5.1.10 Sex determination, 5.1.11 Multiple gene inheritance, and 5.1.12 Development of our understanding of genetics. Each one has a worked solution and a mark scheme showing where the marks go.