Cell cycle

• Cell growth (G1)


  -normal cell reactions, respiration, protein synthesis, photosynthesis

  -cells will increase in size and mass

  -*cells start to increase number of organelles mitochondria, ribosomes

  -plasma membrane and cytoplasm increase in size
• (S phase) DNA replication 


  DNA is copied
• Preparation for mitosis (G2)


  -proteins synthesised for division

  -dna checked for errors by p53 protein

  -if damaged dna repairs it or cells are destroyed
• Cell division 


  Mitosis-prophase, metaphase, anaphase, telophase

  Cytokinesis
• Mitosis


  Process of cell division
• Euchromatin


  Active genes
• Heterochromatin


  Inactive genes
• Who discovered DNA


  Watson, Crick and Franklin
• What does DNA stand for 


  Deoxyribonucleic acid
• Chromatin


  Uncoiled dna in nucleus
• Chromosomes 


  Coilded dna, 2 chromatids
• Chromatids


  Half of a chromosome, coiled
• Centromere 


  Joins chromatids
• Mitosis- prophase 


  • DNA is supercoiled into chromosome
  • Chromatin- supercoiling- chromosome
  • Protein synthesis can not occur whilst supercoiled
  • Identical copied chromatid are attached by a centromere
  • Nuclear envelope breaks down
• Mitosis- metaphase 


  • chromosomes aligned down the equator of cell
  • microtubules grow and attach to the centromeres
  • microtubules put under tension
• Mitosis - anaphase 


  • microtubules contract pulling sister chromatids apart
  • Chromatids form a v shape as they move towards opposite poles in the cell
• Mitosis - telophase 


  • chromatids have arrived at opposite poles of the cell
  • Chromosomes decondese- not visible under light microscope
  • Nuclear envelope reforms
• Cytokinesis


  Cytoplasm and cell membranes divide forming two identical daughter cells
• Binary fission


  • genetic information replicated(nucleoid)
  • Plasmids replicate if applicable
  • Cytoplasm divides approximately in 2
  • Each daughter cell contains a copy of the chromosome
• Cyclins


  Control proteins that activate CDK’s
• Cyclin dependant kinases(cdk)


  Activated by cyclin control cell cycle processes
• What is a tumour 


  Abnormal cell growth form uncontrolled cell division
• What is cancer 


  Disease caused from uncontrolled division of abnormal cells
• Mutagens-agents that change genetic material of an organism 


  • physical - radiation, uv
  • Chemical - substance interact with dna
  • Biological - viruses, bacteria that interfere with dna
• Any mutagen that can cause cancer is called a carciriogen
• Oncogenes


  a gene that has the potential to cause cancer
• proto-oncogenes


  Proteins that stimulate cell cycle, more division
• Tumour suppressor genes


  repress cell cycle, less division
• Proto-oncogenes and TSG’s need to be balanced for an individual to not have cancer
• Benign tumour 


  Remains in its original location

  Not cancerous
• Malignant 


  Invades neighbouring tissue forming secondary tumour

  Causes cancer which spreads through blood or lymph system
• Vascularisation


  Capillaries form around tumours
• Metastasis


  Process of forming secondary tumours
• What happens during cytokinesis in plants 


  • vesicles filled with cell wall components fuse to form a growing cell plate
  • This occurs during telophase
• Unequal cell division


  Usually the cell will divide its subcellular contents equally. Occasionally that is not needed

  • yeast budding
  • Oogenesis=formation of ovum
  • All cells must have 1 mitochondria
• Mitotic index is a method of calculating the rate of mitosis in a tissue sample
• Mitotic index = 100 x (number of cells in mitosis/total number of cells