Question

A twin study of a trait revealed that the concordance for monozygotic twins was 15% but was 85% for dizygotic twins. What would you conclude from the study?

a)The trait has both a significant genetic basis and a significant environmental basis.
b)The trait is mainly genetic in nature with very little environmental basis.
c)The trait is mainly environmental in nature with very little genetic basis.
d)The trait is probably caused by a single gene pair, and it is inherited in an autosomal dominant fashion.
e)The results make no sense and can't be explained, except to assume that the study was flawed.

Answer 1

Option (c), The trait in question is likely mainly environmental with very little genetic basis, as indicated by higher concordance among dizygotic twins compared to monozygotic twins.

Step-by-step explanation:

If a twin study shows that concordance for monozygotic (identical) twins is 15% and 85% for dizygotic (fraternal) twins for a certain trait, one would conclude that the trait is likely mainly environmental in nature with very little genetic basis (option c). This conclusion is the opposite of what one would expect if the trait were genetic because identical twins share the same DNA and thus, would have higher concordance if the trait were mainly genetic.

Research, like the Minnesota Study of Twins Reared Apart, has shown that identical twins tend to have very similar personalities, even when raised apart, indicating a genetic basis for some personality traits. However, it's also acknowledged that many traits are polygenic and influenced by environmental factors. The nature vs. nurture debate highlights that both genetics and environment contribute to the development of traits.

Additionally, Mendelian inheritance patterns demonstrate that not all traits follow a simple dominant or recessive pattern, and human traits can be a complex mix of multiple genetic and environmental factors. Therefore, the unexpected higher concordance rate among dizygotic twins in this scenario could be due to shared environmental factors or a flaw in the study's design or execution.