Chapter 11, Problem 20A

Summary Introduction

To summarize:

The meaning of given information regarding trait inheritance

Introduction:

The environment, which may include sunlight, water and temperature, has an effect on phenotype of an individual. Scientists want to study genetic inheritance of traits rather than environmental contribution of traits. This can be achieved by studying inheritance patterns in twins.

Answer to Problem 20A

Identical twins have higher concordance rate for a particular trait than fraternal twins because identical twins have same genetic makeup.

Explanation of Solution

The percentage of twins who both express a given trait is called a concordance rate.

Identical twins develop from same fertilized egg, so they have the same genetic make- up. Identical twins are genetically the same. If a trait is inherited, both the twins will have the trait. The traits that occur frequently in identical twins are partially controlled by heredity and the traits that are expressed differently in identical twins are influenced by environment.

Fraternal twins develop from two separate eggs that are fertilized by two separate sperms. So they have different genetic information. They will inherit different traits.

Hence identical twins have higher concordance rate for a particular trait than fraternal twins. A large difference between identical twins and fraternal twins shows a strong genetic influence.