Mitosis

• G2 Checkpoint - The cell checks whether all the DNA has been replicated without any damage. If it has, the cell can enter m
• G1 Checkpoint - The cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering the S-Phase.
• The cell cycle consists of a period of cell growth and DNA replication, called interphase, and a period of cell division called M phase.
• The M phase involves mitosis and cytokinesis.
• Interphase is subdivided into three separate growth stages. These are called G1, S and G2
• The cell cycle is regulated by checkpoints. Checkpoints occur at key points during the cell cycle to make sure its ok for the process to continue.
• Interphase - The cell carries out normal functions, but also prepares to divide. The cell's DNA is unravelled and replicated, to double its genetic content. The organelles are also replicated so it has spare one, and its ATP content is increased.
• The stages of mitosis in order are prophase, metaphase, anaphase and telophase.
• Prophase - The chromosomes condense. Tiny bindles of protein celled centrioles start moving to opposite ends of the cell, forming a network of spindle fibers. The nuclear envelope also breaks down.
• Metaphase - The chromosomes attach to the spindle fibers by their centromere and line up along the equator of the cell.
• As mitosis begins, the chromosomes are made of two stands joined in the middle by a centromere. The separate strands are called chromatids.
• There are two strands of DNA because each chromosome has already made an identical copy of itself during interphase. When mitosis is over, the chromatids end up as one-strand chromosomes in the new daughter cells.
• Anaphase - The centromeres divide, separating each pair of sister chromatids. The spindles contract, pulling chromatids to opposite ends of the cell, centromere first.
• Telophase - The chromatids reach the opposite poles on the spindle. They uncoil and become long and thin again. They're now called chromosomes again. A nuclear envelope forms around each group of chromosomes, so there are now two nuclei.
• Cytokinesis - The cytoplasm divides. In animal cells, a cleavage furrow forms to divide the cell membrane. There are now two daughter cells that are genetically identical to each other. This is a seperate process to mitosis.