A researcher investigates the genetic basis of a behavioral trait and finds a concordance rate of 68% for monozygotic (MZ) twins and 31% for dizygotic (DZ) twins.
According to the biological approach, which of the following is the most valid conclusion from this study?
The trait is entirely determined by genetic inheritance (genotype), because the MZ concordance rate is more than double the DZ concordance rate.
The trait has a genetic basis because the MZ rate is significantly higher than the DZ rate, but environmental factors also influence the phenotype because the MZ rate is less than 100%100\%100%.
The trait is entirely determined by environmental factors, because a concordance rate of 68%68\%68% in MZ twins shows that genetic factors are not sufficient to guarantee expression.
The genotype of MZ twins is modified by environmental influences over time, which explains why their concordance rate is below 100%100\%100%.
Practise AQA A Level Psychology Biological approach with exam-style questions for A Level Psychology. 48 questions, matched to the AQA A Level Psychology (7182) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
