1. Cell Divison Describe the process of DNA replication and the evidence for this Explain the phases of the cell cycle and their importance.

2. DNA Replication DNA is read 5’ to 3’ DNA polymerase adds nucleotides together DNA helicase unwinds the DNA by breaking hydrogen bonds. Nucleotides are joined by condensation Complimentary strand is made to the other strand causing semi conservative replication

4. Every dividing tissue cell in the body is always at a stage of the cell cycle. Whether it is at :- STAGES OF MITOSIS Cytokinesis Thus enabling the body to continuously make new body tissue for growth and repair. Prophase Metaphase Anaphase Telophase Interphase } Mitosis

5. Prophase Metaphase Anaphase Telophase The stages of mitosis Interphase

6. PROPHASE The chromatin (unravelled DNA) in the nucleus, condenses to form visible chromosomes. The centrioles that form spindle fibres move to opposite ends of the nucleus. Nuclear membrane begins to break down

7. The structure of a highly condensed, replicated chromosome.

8. METAPHASE The spindle becomes fully developed The chromosomes (chromatid pairs) place themselves onto individual fibres and are aligned along the centre of the spindle The nuclear membrane has now completely disintegrated

9. The Spindle A spindle is a web type structure made up of microtubule fibres. It is essential for mitosis because it arranges the chromosomes into their correct positions in preparation for cell division. Mitotic centre Microtubule A cell at metaphase a spindle

10. ANAPHASE The chromosomes are split into their two chromatids. (This is done by movement of the spindle fibres) The chromatid pairs then travel to opposite ends of the spindle The separated chromatids are now called chromosomes

11. TELOPHASE Two new nuclei are formed when the chromosomes reach the opposite poles of the cell The nuclear membrane is formed. The chromosomes uncoil and disperse in the nucleus, effectively becoming invisible again.

12. REMEMBER! I Interphase P Prophase M Metaphase A Anaphase T Telophase IPMAT

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