Identical twins have exactly the same genome.
A pair of identical twins grow up in different homes. At age 20, one twin has a mass 12 kg greater than the other twin.
Which statement explains the difference in mass?
The twins inherited different alleles from their parents.
A mutation in one twin changed all of the genes for mass.
Mass is controlled by a single gene with a dominant allele.
The twins had different diets and did different exercise.
186 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.