This tutorial will help you to understand that genes play an important role in determining physical traits. These traits helps us to identify the homozygous or heterozygous variety of genes. When the pair of genes are homozygous, they are known as pure bred, i.e they have two copies of the same gene for each trait. For heterozygous variety, they have different gene for each trait. Out of this pair, one will be dominant and other will be recessive.