The ABO blood group is controlled by three alleles: IAI^AIA, IB I^B\,IB and iii.
A geneticist studies the blood groups recorded in two families.
| Family | Blood group of parent 1 | Blood group of one of parent 1's parents | Blood group of parent 2 |
|---|---|---|---|
| 1 | B | O | O |
| 2 | B | O | AB |
Explain which family could have a child with blood group A.
71 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.