What is described by meiosis?

Meiosis is a specialized type of cell division that occurs in sexually reproducing organisms, resulting in the formation of gametes—sperm and eggs. It is characterized by two rounds of division: meiosis I and meiosis II. During meiosis, the chromosomes first duplicate to form sister chromatids, and then the cell divides twice.

In meiosis I, homologous chromosomes are separated into different cells. This reduces the chromosome number by half, resulting in two cells, each with half the original number of chromosomes. Next, in meiosis II, the sister chromatids are separated, leading to a total of four genetically unique cells at the end of the process. Thus, the key aspect of meiosis is that it involves two divisions after one round of chromosome duplication, ultimately resulting in four haploid cells.

This distinguishes meiosis from mitosis, which involves a single division leading to two genetically identical cells. Therefore, the correct answer captures the essential nature of meiosis by highlighting the duplicated chromosomes and the two divisions that result in four cells.