Final answer:
Meiosis is a type of cell division responsible for reducing the chromosome number by half to form haploid gametes, leading to genetic diversity in sexually reproducing organisms.
Step-by-step explanation:
The process that occurs in the formation of sex cells, in which the number of chromosomes is reduced by half, is known as meiosis. This type of cell division is crucial for sexual reproduction, as it leads to the production of haploid gametes—sperm and eggs in animals, which contain only one set of chromosomes. Therefore, when fertilization occurs, the resulting zygote has the appropriate diploid number of chromosomes.
Meiosis consists of two rounds of nuclear division: meiosis I and meiosis II, which result in four genetically unique haploid cells. During meiosis I, homologous chromosomes are separated, and in meiosis II, sister chromatids divide, akin to what happens during mitosis. Its unique features such as crossing-over during prophase I and random segregation of chromosomes contribute to genetic diversity in sexually reproducing populations.