Introduction to Cell Division

Summary:

This Introduction to Cell Division note explains that cell division is crucial for growth, repair, and reproduction in living organisms. The cell cycle has three stages: Interphase, Mitosis, and Cytokinesis. Interphase, where a cell spends most of its life, involves growth, DNA duplication, and division preparation. It is split into G1 (growth and function), S (DNA replication), and G2 (division readiness). Mitosis involves distributing DNA copies to two daughter cells, following a sequence of Prophase, Metaphase, Anaphase, and Telophase. Sister chromatids, identical DNA strands, move around the cell before being separated and enclosed in new nuclei. Cytokinesis, the final step, is the division of the cytoplasm, forming two new cells. In addition to mitosis, meiosis is another form of cell division, producing gametes (sex cells) with half the chromosome number, promoting genetic diversity. It involves two rounds of cell division and features synapsis (pairing of homologous chromosomes), crossing over (exchange of genetic material), and reduction division, resulting in four genetically unique haploid cells.

Excerpt:

Introduction to Cell Division

Cell Division
• All cells come from other living cells.
• And based on cell theory, cells cannot reproduce, i.e. they multiply by dividing or duplication.
• we (and other living things) grow because our cells get bigger and the number of cells in our body gets larger.
– A single cell divides into two cells.
– Two cells divide into four, etc.
• Cells must also divide because old cells die and need new cells to replace them!

The Cell Cycle

• Cell cycle – regular sequence of growth and division that eukaryotic cells undergo.
– Prokaryotic cells undergo binary fission
• Divided into three main stages:
– Interphase – cell grows into its mature size, makes a copy of its DNA, and prepares for division.
– Mitosis – one copy of the DNA is distributed into each of its daughter cells
– Cytokinesis – the cytoplasm divides, and organelles are distributed into the two new cells