Genes and Chromosomes as the Sites of Change

Abstract

Biological evolution is dependent on differential selection of phenotypes. This in turn requires that phenotypes should differ. Changes in phenotype are reflections of changes in the hereditary material. Despite the care which is taken in the replication of the DNA, changes do take place from generation to generation and these are known as mutations. Mutations can either have effects only on one gene or be so drastic as to affect whole chromosomes or parts of chromosomes.