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Cell Division - OCR AS Biology

Presentation going through the specification requirements related to cell division (unfinished)

Jessica Fallows

on 15 March 2013

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Transcript of Cell Division - OCR AS Biology

Mitosis Interphase is the period leading up to the dividing of the cell in mitosis Interphase In prophase, the chromosomes supercoil. They can now be seen through a light microscope as two sister chromatids joined at the centromere. Prophase The sister chromatids attach to the spindle fibres by their centromere Metaphase Mitosis only occupies a small percentage of the cell cycle. Much of it is actually in interphase. The Cell Cycle 90% of a cell's cycle can be spent in interphase. It is split into three sections: G1 S G2 G1 S G2 The cell grows to prepare for cell division The cell synthesises and duplicates it's DNA The cell continues to grow in preparation for mitosis After the G2 phase the cell begins mitosis. Cell Division This presentation covers the following points on the specification:
state that mitosis occupies only a small percentage of the cell cycle and that the remaining percentage includes the copying and checking of genetic information.
describe, with the aid of diagrams and photographs, the main stages of mitosis.
explain the meaning of the term homologous pair of chromosomes.
explain the significance of mitosis for growth, repair and asexual reproduction in plants and animals. Why is Mitosis
important? Asexual Reproduction many multicellular organisms rely on mitosis for asexual reproduction and it is the sole form of reproduction for many single-celled organisms. Growth Multicellular organisms grow by producing new extra cells. Each new cell is genetically identical to the parent cells and so can perform the same functions. Repair Damaged cells need to be replaced by new ones that need to be identical so as to perform the same functions Replacement This maintains the organism e.g. red blood cells and skin cells are replaced with new ones Genetic information is checked at numerous stages during interphase to ensure that there are no errors here is an onion root cell during interphase chromatin nucleus The nuclear envelope breaks down and disappears The centriole divides into two, and moves to opposite ends of the cell to form the spindle (protein threads) here is an onion root cell during prophase sister chromatids no nuclear envelope After prophase has occured the cell then moves onto metaphase Anaphase Telophase Cytokinesis The chromosomes move towards the centre of the spindle region and align along the spindle equator. here is an onion root cell during metaphase spindle fibres sister
chromatids after metaphase the cell goes into anaphase Homologous pair of chromosomes Chromosomes which contain the same genes but different alleles
- one from the mother
- one from the father Mother Father e.g.
gene for eye colour brown eyes blue eyes
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