Summary
Highlights
In the initial growth phase, the cell increases in size and the number of its subcellular structures, like mitochondria and ribosomes. Following growth, the DNA is duplicated to ensure each new cell receives a complete set of genetic material.
Multicellular eukaryotic organisms constantly require new cells for growth, development, and repair. This process is called the cell cycle, starting from when a cell is made until it divides into two new cells. The cell cycle has three main stages: growth, DNA replication, and mitosis and division (cytokinesis).
Normally, DNA is spread out in long strings. However, when a cell prepares for division, DNA condenses into coiled structures called chromosomes, which contain many genes. Eukaryotic cells have two copies of each chromosome; humans have 23 pairs (46 total). During preparation for division, each chromosome duplicates, forming an X-shape where the duplicate remains attached to the original.
During mitosis, all 46 chromosomes align at the center of the cell. Spindle fibers attach to each half of the X-shaped chromosomes and pull them to opposite sides (poles) of the cell, effectively breaking them in half and ensuring equal distribution of genetic material.
After the genetic material is divided, the cell membrane and cytoplasm pinch apart, resulting in two identical daughter cells. Each daughter cell contains the same DNA as the parent cell, allowing them to contribute to growth, development, or repair and restart the cell cycle.