Mendel discovered that when crossing white flower and purple flower plants, the result is not a blend. Rather than being a mix of the two, the offspring was purple-flowered. He then conceived the idea of heredity units, which he called "factors", one of which is a recessive characteristic and the other dominant. Mendel said that factors, later called genes, normally occur in pairs in ordinary body cells, yet segregate during the formation of sex cells. Each member of the pair becomes part of the separate sex cell. The dominant gene, such as the purple flower in Mendel's plants, will hide the recessive gene, the white flower.
Mendel stated that each individual has two factors for each trait, one from each parent. The two factors may or may not contain the same information. An individual possesses two alleles for each trait; one allele is given by the female parent and the other by the male parent. They are passed on when an individual matures and produces gametes: egg and sperm. When gametes form, the paired alleles separate randomly so that each gamete receives a copy of one of the two alleles.
Mendel summarized his findings in two laws: the Law of Segregation and the Law of Independent Assortment.
This what happens in meiosis which forms the egg or the sperm. These then combine to form a new individual which has a new mix of traits from the parents.