Why do monozygotic twins have different phenotypes?
A) They have different genotypes.
B) They have nonshared environments.
C) They have the same environments but different genes.
D) They have only minor phenotypic variation across a few physical traits but no differences in psychological traits.

Question

Quizplus · Accepted Answer

Monozygotic twins have the same genotype because they come from the same fertilized egg that splits into two embryos. However, they can have different phenotypes due to nonshared environments such as differences in nutrition, experiences, and epigenetic modifications. Even small differences in the environment can cause differences in gene expression, leading to different phenotypic traits. Therefore, option B is the correct answer. Options A and C are incorrect because monozygotic twins have identical genotypes and share the same environment, respectively. Option D is incorrect because monozygotic twins can have significant differences in psychological traits as well.

Why Do Monozygotic Twins Have Different Phenotypes