A synapsis is the pairing of two chromosomes during meiosis. This process allows for the chromosomes to crossover and genetic material is exchanged. This exchange leads to varying genetics in organisms that reproduce sexually.
A synapsis occurs when the chromosomes form a pair of sister chromatids during the first phase of meiosis, which is referred to as prophase I. These sister chromatids connect to one another through RNA and protein combinations. During this process, they interlock and coil together. This is the crossover process. As this phase continues, the homologous chromosome pairs migrate toward either the left or right side of the cell. As this process moves to anaphase I, the synapsis ends. As it ends, the chromosome pairs separate. In later phases, these chromosomes are picked up by separate daughter cells.
After the synapsis has ended, meiosis II occurs. In this stage, some of the processes that began in meiosis I with the synapsis are continued. The cells from meiosis I separate and gametes are formed. These gametes play a significant role in genetic variability through the assortment of the 23 chromosomes. This, along with the exchange of genetic information during the crossover in synapsis, leads to variability within individuals.