6.4 Lesson 4: Cell Division
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- After the DNA has replicated in the nucleus of the cell and then re-coiled into a chromosome, the cell begins to divide and multiply. This cell multiplication allows for replacement of old cells, tissue repair, growth (such as hair growth) and development.
- Mitosis and meiosis are two types of cell division.
- Mitosis is cell division that results in the duplication of cells, the daughter cells being genetic copies of the parent cell. The number of chromosomes are equal in each cell (46). The chromosomes divide, one set staying in the ‘parent’ cell and the other set moving into the new ‘daughter’ cell.
- In sex cells (eggs and sperm), the cells divide by meiosis. Meiosis is more complex than mitosis as it involves two divisions of genetic material. The sex cells end up with half the number of chromosomes than the original cell that they arose from (23 in each). This enables the union of two sex cells at fertilization to produce a new embryo with the correct number of chromosomes (23 + 23 = 46).
