Two parents both have blood group A. They have a child with blood group O.
What proportion of all their children is expected to have blood group A and be heterozygous?
12\frac{1}{2}21
14\frac{1}{4}41
34\frac{3}{4}43
111
43 exam-style questions on Edexcel GCSE Biology 3.3 Inheritance, covering 3.3.1 Gregor Mendel and the basis of genetics, 3.3.2 Alleles and inherited characteristics, 3.3.3 Monohybrid inheritance, 3.3.4 Determination of sex at fertilisation, 3.3.5 Outcomes from monohybrid crosses, 3.3.6 Inheritance of ABO blood groups, 3.3.7 Inheritance of sex-linked disorders, and 3.3.8 Multiple genes and phenotypic features. Each one has a worked solution and a mark scheme showing where the marks go.