Mendelian inheritance
1. Factors, later called genes, normally occur in pairs in ordinary body cells, yet separate during the formation of sex cells. This happens in meiosis, the production of gametes. Of each pair of chromosomes, a gamete only gets one. The factors (genes) determine the organism's traits, and are inherited from its parents. As the pair of chromosomes separate, each gamete only receives one of each factor. This Mendel called the Law of segregation.