Therefore, the possible number of genetically different pigs can be much larger than the total number of pigs being raised on the nation's farms. Gamete formation and fertilization. The random transfer of chromosomes and their genes to forming gametes is called random segregation. Random segregation is a major cause of genetic differences among related individuals. Differences in genetic makeup are often referred to as genetic variation.
Traits showing a large amount of genetic variation have a better chance of responding to selection.
If a large amount of genetic variation is present in a population, some animals will carry many favorable genes while others will have more undesirable genes for a given trait. If individuals with favorable genes can be identified, there is an increased likelihood that those individuals will pass those favorable genes on to their offspring. The specific genes that reside in the gene pairs that control a trait is called the animal's genotype. For a given gene pair, the two genes can be alike or different. A homozygous gene pair has two identical genes while a heterozygous gene pair has different genes.