What is the logic behind a twin study?
A) If monozygotic twins, who show 100% genetic similarity, have greater behavioral concordance on a given trait than dizygotic twins do, that trait is at least partially genetically determined.
B) If dizygotic twins, who show 100% genetic similarity, have greater behavioral concordance on a given trait than monozygotic twins do, that trait is at least partially genetically determined.
C) If monozygotic twins, who show 100% genetic similarity, have greater behavioral concordance on a given trait than dizygotic twins do there is a gene for the trait that these twins share.
D) If dizygotic twins, who show 100% genetic similarity, have greater behavioral concordance on a given trait than monozygotic twins do there is a gene for the trait that these twins share.

Question

Quizplus · Accepted Answer

The logic behind a twin study is to compare the concordance rates of a trait or behavior in monozygotic (identical) and dizygotic (fraternal) twins, who share different degrees of genetic similarity. If monozygotic twins, who have the same DNA, show greater concordance on a certain trait than dizygotic twins, it suggests that the trait has a genetic component. This is because monozygotic twins share all of their genes, while dizygotic twins share approximately 50% on average. Therefore, any differences in behavioral concordance between the two types of twins can be attributed to differences in their genetic makeup. Choice B, C, and D are incorrect because they do not accurately reflect the principle of genetic determination in twin studies.

What Is the Logic Behind a Twin Study