mitosis

• what is the order of the cell cycle?

  • interphase
  • G1
  • S
  • G2
  • Mitosis
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
  • Cytokinesis
• what is the difference between mitosis and meiosis?

  1. Mitosis is used for tissue replacement and growth. Meiosis is used to produce gametes
  2. Mitosis: each new cell is genetically identical to the original cell. Meiosis: each gamete contains only half of the genetic material of the parent cell
• what is a chromosome?

  contain genetic material, also known as DNA
• what is a centromere?

  The region on a chromosome that joins 2 sister chromatids together at the point where the spindle fibres attach
• what is a centriole?

  A centriole is a small cylindrical organelle found in animal cells that plays a role in cell division and the organization of the cytoskeleton.
• what is the importance of mitosis?

  1. maintains the chromosome number
  2. growth
  3. repair
  4. asexual
• what is growth important for mitosis?

  so that all the cells from the zygote are identical
• why is repair important for mitosis?

  so if the cells are damaged, new cells are produced and have an identical structure and function
• what is the cell cycle?

  a sequence of reactions that result in the growth of the cell and replication of the genetic material to make 2 identical daughter cells
• what are the stages of mitosis?

  1. prophase
  2. metaphase
  3. anaphase
  4. telophase
• what is prophase?


  • chromosomes condense to become visible
  • The two centrosomes move towards opposite poles
  • Spindle fibres begin to emerge from the centrosomes 
  • The nuclear envelope  breaks down into small vesicles

  
• what is metaphase?


  • Chromosomes line up at the equator of the spindle so they are equidistant to the two centrosome poles
  • Spindle fibres reach the chromosomes and attach to the centromeres

  
• what is anaphase?


  • The sister chromatids separate at the centromere 
  • Spindle fibres begin to shorten
  • The separated sister chromatids are pulled to opposite poles by the spindle fibres

  
• what is telophase?


  • Chromosomes arrive at opposite poles and begin to decondense
  • Nuclear envelopes begin to reform around each set of chromosomes
  • The spindle fibres break down

  
• what is cytokinesis?

  the cytoplasm divides forming two genetically identical cells 
• what is interphase?

  the stage in the life cycle of a cell where the cell grows and DNA is replicated.
• what are the 3 phases in interphase?

  • G1
  • S
  • G2
• what is G1?

  • cell grows and receives a signal to divide
• what is S?

  • synthesis of new DNA
• What is G2?

  • further cell growth
  • Short gap before mitosis
  • error checking a newly synthesised DNA
• how long does the cell cycle lasts for?

  24 hours
• how long does mitosis last for?

  1-2 hours
• how long does the interphase last for?

  • lasts up to 23 hours
  • this includes 10-12 hours of DNA synthesis
• what is a tumour?

  a mass of cells/tissues that undergo uncontrolled mitosis
• what is cancer?

  • Cancer is a disease of uncontrolled cell division. 
• how is the development and progress of cancer linked to a series of changes in the activity of the cell cycle?

  • due to inhibitors
  • due to positive regulation of cell division which can lead to cancer if too active
  • due to mutations in the genes that encode cell cycle regulators proteins
• What are mutated genes that cause cancer are referred to as?

  oncogenes
• what are the causes of cancer?


  • d
• What are the risk factors associated with cancer?

  • Carcinogens - chemicals or radiation  (nicotine, alcohol, x-rays)
  • Sun exposure – UV radiation is linked to skin cancer 
  • Viruses
  • Age – cells get damaged over time. This damage builds up as we age and can lead to cancer. 
  • Alcohol – (breast, bowel, liver, mouth & throat, oesophagus and stomach cancer. )
  • Body weight & diet 
  • Smoking – (lung cancer )
  • Inherited genes e.g. BRCA. This gene increases the chances of breast cancer and so some women will decide to have a mastectomy. 
• what is Benign?

  a mass of cells that does not invade surrounding tissue. It forms a tumour which is non-cancerous therefore it is not strictly speaking called a cancer
• What is Malignant?

  • a tumour made of cells that invade nearby tissues and spread to other parts of the body. This is a cancer.
• what is Metastasis?

  • the process by which cancerous cells spread from their place of origin and form secondary tumours.
• what does cancer treatment involve?

  •  involves killing dividing cells by blocking part of the cell cycle
• what are cancer treatments?

  • DNA - disrupts the cell cycle but can disrupt normal cells
  • surgery - only if the tumour is operable
  • chemotherapy - chemicals that target actively dividing cells
  • radiotherapy - target the tumour by radiation which makes breaks in the DNA
• what is cell division called in prokaryotic cells?

  Binary fission
• what is binary fission?

  • circular DNA molecule replicates and both copies attach to the cell membrane
  • plasmids also replicate
  • cytoplasm divides into two
• describe binary fission in bacteria?

  • replication of circular DNA
  • replication of plasmids
  • division of cytoplasm to produce daughter cell
• why can't viruses undergo cell division?

  • viruses are non-living
  • so they replicate by attaching by to their host cell
• describe viral replication?

  • attachment proteins attach to receptors
  • viral nucleic acid enters cell
  • nucleic acid replicates in cell
  • cell produces viral proteins/capsids/enzymes
  • virus assembled and released from cell
• difference between binary fission and mitosis?

  Binary fission: occurs among prokaryotes, doesn't include spindle formation and sister chromatids, faster cell division, bacteria chromosomes attach to the membrane

  Mitosis: occurs among eukaryotes, does include spindle formation and sister chromatids, slower division, bacteria chromosomes don't attach to the membrane