Polydactyly is caused by a dominant allele, $P$. Two parents both have polydactyly. They have a child without polydactyly.
Assume the condition is controlled by this gene alone and no new mutation occurs. Which statement must be correct?
Both parents are homozygous; the child inherited one recessive allele from each parent.
Both parents are heterozygous; the child inherited one dominant allele from each parent.
Both parents are heterozygous; the child inherited one recessive allele from each parent.
Both parents are homozygous; the child inherited one dominant allele from each parent.
76 exam-style questions on AQA GCSE Biology 6.1 Reproduction, covering 6.1.1 Sexual and asexual reproduction, 6.1.2 Meiosis, 6.1.3 Advantages and disadvantages of sexual and asexual reproduction, 6.1.4 DNA and the genome, 6.1.5 DNA structure, 6.1.6 Genetic inheritance, 6.1.7 Inherited disorders, and 6.1.8 Sex determination. Each one has a worked solution and a mark scheme showing where the marks go.