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all cells arise from other cells - Coggle Diagram
all cells arise from other cells
prokaryote replication:
-binary fission:
1- bacterial RNA replicates
2- DNA binds to a section of bacterial membrane
3- membrane elongates pulling the DNA to either side
4- membrane contracts for 2 new cells
-virus replication:
1- attaches to host cell
2- injects its RNA
3- uses cellular machinery to replicate
4- host is overfilled and bursts
cancer:
-controlling the cell cycle:
-the cell cycle is controlled at 3 checkpoints
-these checkpoints ensure that the stages of the cell cycle have been completed correctly
-the cell cycle is controlled by signals that tell the cell that it needs to divide if there was a need for growth or repair
-these proteins are produced by genes called proto-oncogenes
-if DNA damage is detected or the cell cycle hasnt been completed correctly it will stop at the checkpoint
-the genes that control this process are tumour-supressor genes
-treating cancer:
often involve killing cells by blocking the cell cycle to stop the cell dividing by:
-preventing DNA replication
-inhibiting spindle formation and therefore metaphase
-side effects:
-the chemicals that cure cancer also target all dividing cells
-greatest effect on most rapidly dividing cells:
-hair loss and reduced white blood cells
-"the result of mutations to the genes that regulate the cell cycle and mitosis this leads to uncontrollable growth and division of cells
-benign tumour- a mass of abnormal cells that divide when there is no need for growth or repair
-malignant tumour- a tumour that tends to spread to other areas via the blood or lymph systems
-metastasis- when secondary tumours form called metastatses
-proto-oncogenes- normally induced cells to divide in a certain way
-tumour supressor genes- stop the cell cycle when genes are mutated
mitosis and the cell cycle:
-what is the cell cycle:
-the cell cycle is the regular cycle of cell division, seperated by periods of growth
-only some cells in multicellular organisms retain the ability to divide
-interphase:
-the longest part of the cell cycle
-chromosomes not visable chromatin dispersed through the nucleus
-G1= cell growth (organelle replication)
-S= DNA replication
-G2= preparation for mitosis (ATP, protein synthesis)
-nessecary for:
-asexual reproduction
-growth
-replacement of worn out cells
-prophase:
-chromosomes become thicker and shorter
-centrioles where present, divide and move to cell poles
-spindle fibres form from each centriole ofr the spindle apparatus
-nuclear membrane disintergrates and the nucleolus disappears
-metaphase:
-chromosomes visable as pairs of chromatids joined at the centromere, arrange at the equator
-they attach to the spindle fibres at the centromere
-anaphase:
-a very rapid stage
-centromere divides, spindle fibres contract and shorten, pulling the chromatids to opposite poles
-energy provided by mitochondria around spindle fibres
-telophase:
-chromosomes have reached the poles, they uncoil and lengthen to become chromatin
-nucleoli reappear and the nuclear membrane reforms
-cytokinesis:
-occurs by the cleavage of the cell membrane the cytoplasm then divides forming 2 daughter cells
-in plant cells the cell plate forms across the cell equator and new cell wall is laid