New News Biology #4

Cell Cycles, Chromosomes & Mitosis

Plants, humans and animals all need a continuous supply of new cells for:

Development

Growth

Repair (only comes after the previous)

Note: the first two are mostly true in younger organisms.

The Cell Cycle (also known as “the life of a cell”)

Growth: the cell increases in size & increases the number of sub-cellular structures inside itself

DNA Replication

Chromosomes replicate within to form “X” shapes (after replication but before division, there are 46 chromosomes inside the cell).

When it is time to divide, cell fibres pull apart the “X”-shaped chromosomes to the two separate poles/ends of the cell.

Division (Cytokinesis/Mitosis)

Two daughter cells are created, identical to their parent, and each have the normal amount of 23 chromosomes.