Chapter 19, Problem 18P

Summary Introduction

To analyze:

Human MZ and DZ are the twin pairs of the same sex reared together are studied and the following concordance values are identified for various traits. Depending on the values shown in the table, explain the relative importance of genes versus the influence of environmental factors for each trait.

Trait	Concordance
	MZ	DZ
Blood type	$100$	$65$
Chicken pox	$89$	$87$
Manic depression	$67$	$13$
Schizophrenia	$72$	$12$
Diabetes	$62$	$15$
Cleft lip	$51$	$6$
Club foot	$40$	$4$

Introduction:

Monozygotic twins (MZ) are the ones who prepared from one zygote, which splits and forms two embryos. In dizygotic twins (DZ), each twin develops from each egg is fertilized by a dissimilar sperm and a separate egg. To estimate the influence of genes on phenotypic variation, the study of identical twins reared together can be carried out. In such studies, concordance is measured. Concordance is the percentage of twin pairs in which both members of the pair have the same phenotype for a trait. Concordance frequency gives a general picture of the overall influence of genes on phenotypes.