Unit 7: Cell Division
- Page ID
- 3766
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- 7.2: The Cell Cycle
- A eukaryotic cell cannot divide into two, the two into four, etc. unless two processes alternate: doubling of its genome (DNA) in S phase (synthesis phase) of the cell cycle; halving of that genome during mitosis (M phase).
- 7.3: Mitosis
- When a eukaryotic cell divides into two, each daughter or progeny cell must receive a complete set of genes (for diploid cells, this means 2 complete genomes, (2n) a pair of centrioles (in animal cells) some mitochondria and, in plant cells, chloroplasts as well some ribosomes, a portion of the endoplasmic reticulum, and perhaps other organelles,
- 7.4: Polyploidy
- Cells (and their owners) are polyploid if they contain more than two haploid (n) sets of chromosomes; that is, their chromosome number is some multiple of n greater than the 2n content of diploid cells. For example, triploid (3n) and tetraploid cell (4n) cells are polyploid.
- 7.5: Endoreplication
- Endoreplication is the replication of DNA during the S phase of the cell cycle without the subsequent completion of mitosis and/or cytokinesis. Endoreplication is also known as endoreduplication. Endoreplication occurs in certain types of cells in both animals and plants.
- 7.6: Sex Chromosomes
- The nuclei of human cells contain 22 autosomes and 2 sex chromosomes. In females, the sex chromosomes are the 2 X chromosomes. Males have one X chromosome and one Y chromosome. The presence of the Y chromosome is decisive for unleashing the developmental program that leads to a baby boy.
- 7.7: Meiosis
- Mitosis produces two cells with the same number of chromosomes as the parent cell. Mitosis of a diploid cell (2n) produces two diploid daughter cells. If two diploid cells went on to participate in sexual reproduction, their fusion would produce a tetraploid (4n) zygote. The solution for this problem is Meiosis.
Thumbnail: Life cycle of the cell. (CC BY-SA 4.0; BruceBlaus).