The lifespan of different cell types varies, and some cells such as nerve cells never divide once they are formed. However, this represents the lifespan of a typical cell. Normal body cells have a complete set of chromosomes. If normal body cells from mom and dad fused to form a baby, the fertilized egg would have twice as many chromosomes as it should. This is called synapsis.
Homologous chromosomes contain the matching alleles donated from mother and father.
This process allows for a genetic shuffling of the characteristics of the two parents, creating an almost infinite variety of possible combinations. See the close-up diagram below. The paired chromosomes line up. The final outcome is four cells, each with half of the genetic material found in the original. In the case of males, each cell becomes a sperm.