What occurs during the first stage of meiosis?

Meiosis is made up of two distinct phases: meiosis I and meiosis II. Each of these phases is further subdivided into prophase, metaphase, anaphase, and telophase.

The initial phase of meiosis is known as prophase I.

Prophase I is further subdivided into sub-stages such as leptotene, zygotene, pachytene, diplotene, and diakinesis. Pairing of homologous chromosomes occurs in early prophase.

During the pachytene stage, homologous chromosome pairing takes place, and is followed by chromosome shortening and thickening. During the pachytene stage, crossing over takes place.

During the diplotene stage, the crossing site is visible as a chiasma formation.

Diakinesis produces bivalents with distinct shapes based on the quantity and location of crossing over.

During the first stage of meiosis, known as prophase I, homologous chromosomes pair up and exchange genetic material through a process called crossing over. This results in genetic recombination, increasing genetic diversity. Additionally, the nuclear envelope dissolves, and spindle fibers begin to form.