Which of the following primarily occurs during Meiosis I?

The halving of chromosome number is a defining characteristic of Meiosis I. During this stage of meiosis, homologous chromosomes are separated and distributed into two daughter cells. Each homologous pair aligns at the metaphase plate and, upon separation during anaphase, reduces the chromosome number by half. This is crucial for sexual reproduction, as it ensures that gametes (sperm and egg cells) contain only one set of chromosomes, providing the opportunity for genetic diversity when fertilization occurs.

While DNA replication does happen before meiosis begins, it does not occur specifically during Meiosis I. The separation of sister chromatids occurs later in Meiosis II, not during Meiosis I. Finally, the formation of a zygote takes place after fertilization, long after the events of meiosis are complete. Therefore, recognizing the specific events that occur during each stage of meiosis is essential for understanding the overall process and its implications for genetic inheritance.