Heterozygosity

Definition of Heterozygosity: the possession of two different alleles of a particular gene or genes by an individual. The degree of heterozygosity is defined as the proportion of sites on the chromosome at which two randomly chosen copies differ in DNA sequence. This is the common definition for Heterozygosity, other definitions can be discussed in the article

The opposite of heterozygosity is homozygosity, in which a harmful mutation can cause disease because both gene alleles are defective.