Final answer:
Synapsis and the formation of tetrads take place during Prophase I of meiosis. Homologous chromosomes are bound by a synaptonemal complex to form tetrads, which align independently at the metaphase plate, contributing to genetic diversity.
Step-by-step explanation:
Synapsis and the formation of tetrads occur during Prophase I of meiosis. At this stage, homologous chromosomes come together to form a synapse, tightly bound by a protein lattice known as the synaptonemal complex and by cohesin proteins at the centromere, leading to the formation of tetrads. Each tetrad comprises four sister chromatids of homologous chromosomes.
Once tetrads are formed, they move to line up at the metaphase plate, located at the midway point between the two poles of the cell. This arrangement contributes to genetic diversity because there is an equal chance of a microtubule fiber encountering either maternally or paternally inherited chromosomes during separation, and the orientation of each tetrad is independent of other tetrads. The chiasmata, which are points where chromosomes exchange genetic material during crossover, maintain contact between the homologues until they segregate.