Mitosis

• Mitosis has 4 main stages: prophase, metaphase, anaphase, telophase
• If no chromosomes are visible, the cell is in the interphase
• In the prophase, the DNA coils and chromosomes become visible. The nuclear membrane breaks down and centrioles migrate to poles and start to form spindle fibres.
• In the metaphase, spindles bind to centrosome of each chromosome. Chromosomes are guided to the cell equator.
• In the anaphase, spindles contract and fracture the chromosomes at the centrosome. Each chromosome is pulled to opposite poles of the cell.
• In the telophase, nuclear membranes reform and chromosomes disperse. Cytokinesis begins - both daughter cells are exact copies of the parent cell.
• In the interphase, the cell grows and DNA replicates.
• DNA replication is a semi-conservative process.
• DNA helicase unwinds the DNA and breaks the hydrogen bonds between complementary base pairs (Adenine + Thymine, Cytosine + Guanine).
• Free nucleotides naturally form hydrogen bonds with the exposed unpaired bases on the single DNA strands.
• DNA polymerase catalyses the condensation reaction that joins the nucleotides by forming phosphodiester bonds.