A study of monozygotic (MZ) twins reveals that although both twins carry the gene variant associated with high risk of type 2 diabetes, only one twin actually develops the condition after a lifetime of a high-sugar diet, while the other twin remains healthy due to active lifestyle choices.
Which of the following statements best explains this outcome in terms of the biological approach?
Both twins share the same genotype, but their phenotypes differ because environmental factors influenced gene expression.
The twins have different genotypes because environmental factors mutated their inherited DNA sequence, leading to different phenotypes.
The healthy twin possesses a dominant genotype, whereas the diabetic twin has expressed a recessive phenotype due to diet.
The twins have different phenotypes because monozygotic twins share only 50%50\%50% of their genetic makeup, resulting in different genetic predispositions.
248 exam-style questions on AQA A Level Psychology Approaches in Psychology, covering Learning approaches, Cognitive approach, Biological approach, Psychodynamic approach (A-level only), Humanistic Psychology (A-level only), and Comparison of approaches (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.