cell cycles chromosomes mitosis

• All multicellular eukaryotic organisms require a continuous supply of new cells for growth, development, and repair
• Cell cycle: life cycle of a cell from the time it is made to the time it divides into two new cells
• Three main stages of the cell cycle:

  • Growth
  • DNA replication
  • Mitosis and division (cytokinesis)
• During growth stage, the cell increases in size and the number of subcellular structures it contains
• DNA is duplicated during DNA replication stage so that each new cell will have a full set of DNA
• DNA condenses into chromosomes during preparation for division
• Chromosomes are packets of DNA containing genes that control different characteristics
• Eukaryotic cells have two copies of each chromosome, one from the mother and one from the father
• Humans have 23 pairs of chromosomes, totaling 46 chromosomes
• During division, all 46 chromosomes line up along the center of the cell
• Spindle fibers attach to each chromosome and pull them to opposite sides of the cell, breaking them in half
• Cytokinesis: cell membrane and cytoplasm pull apart, forming two daughter cells with the same DNA as the parent cell