Monozygotic twin concordance values are less than 100% in both bipolar disorder and schizophrenia.This suggests that these disorders ____.
A) are strictly polygenic
B) have environmental components
C) are X-linked
D) genetically dominant
E) are not genetically based

Question

Monozygotic twin concordance values are less than 100% in both bipolar disorder and schizophrenia.This suggests that these disorders ____.
A) are strictly polygenic
B) have environmental components
C) are X-linked
D) genetically dominant 
E) are not genetically based

Quizplus · Accepted Answer

The fact that monozygotic twin concordance values are less than 100% suggests that environmental components play a role in the development of bipolar disorder and schizophrenia, in addition to genetic factors. This rules out choices C, D, and E. The disorders are likely polygenic, which is consistent with choice A, but this alone does not account for the observed twin concordance values. Therefore, choice B is the best answer.

Monozygotic Twin Concordance Values Are Less Than 100% in Both