Meiosis 1: Prophase 1
Diagram of prohpase 1.
In prophase I the chromosomes become visible. However, unlike prophase of
mitosis, the two chromosomes combine or synapse to form tetrads. Tetrads are
also known as bivalents because they contain two pairs of chromosomes. At this
point the chromosomes cross over at points called chiasmata. Crossing over
allows the chromosomes to exchange genetic material, allowing for more different
combinations of genetic material. As in the prophase of mitosis the nuclear
envelope disperses, the spindle moves into the center, and the tetrads become
connected to the spindle fibers by kinetochores.
Continue on to Meiosis 2: Metaphase 1