90 Chapter 3 • The Chromosomal Basis of Inheritance 3.3 Mitosis and meiosis When cells divide, the chromosomes must also make copies of themselves (replicate) to maintain the appro-priate chromosome number in the descendant cells. In eukaryotes, the chromosomes replicate in two main types of nuclear divisions, called mitosis and meiosis . Even though these two types of divisions are quite dif-ferent and have different functions, some of the molecu-lar features are held in common. Three common molec-ular processes to focus on are DNA replication , adhesion of replicated chromosomes, and orderly movement of chromosomes into descendant cells. Mitosis is the nuclear division associated with the asexual division of cells. In multicellular organisms mito-sis takes place during the division of somatic cells, the cells of the body. In single-celled eukaryotes such as yeasts, mitosis occurs in the cell divisions that cause population growth. Since asexual cell division is aimed at straightforward reproduction of cell type, it is neces-
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