cancer

• Oestrogen stimulates cell division in breast cells.
• Benign tumours are non-cancerous and grow slowly. They’re covered in fibrous tissue that stops them from invading other parts of the body.
• what are malignant tumours?

  mass of undifferentiated cells that cause uncontrolled cell division and are cancerous. they spread to surrounding tissues and form new tumours
•   Give one reason for the change in death rate from malignant skin tumours with increasing age.

  • cancer takes a while to develop
  • more exposure to UV
  • immune system less effective in older people
• The data for fair-skinned and dark-skinned people were collected separately.Explain why skin colour was a factor likely to affect the death rate.

  • darker skin contains more melanin which stops burning
  • therefore darker people will be less likely to develop skin cancer
•   Explain the presence of bile in the colon.

  secreted by liver

  bile passes from small intestine to colon
• Human cells contain genes that control their growth and division. One of these genes codes for a protein that prevents cell division. The substances formed from bile steroids by Clostridium bacteria may cause gene mutation. Describe and explain how these substances could cause colon cancer.

  • change in base sequence occurs causing mutation eg, deletion meaning mRNA changes which effects amino acid sequence and gene function
  • This could cause uncontrolled cell division
• Give one way in which a benign tumour differs from a malignant tumour.

  • benign doesn't invade surrounding tissues
  • doesn't cause cancer
  • doesn't form new tumour
•  Describe two ways in which both types of tumour may cause harm to the body.

  • could cause a blockage
  • exert pressure on surrounding organs and damage them
• Explain the link between sunbathing and skin cancer.

  sun’s radiation contains ultra violet radiationthis causes mutation of genes which control division
• Suggest why fair-skinned people are at a greater risk of skin cancer than dark-skinned people when sunbathing.

  have less melanin in skin which protects against UV
• Suggest why people with a family history of cancer are at a greater risk of cancer than those with no family history of cancer.

  cancer has genetic component so have a genetic predisposition to developing it as inherited the gene
• Describe how altered DNA may lead to cancer.

  • DNA altered by mutation which could change base sequence of TSG
  • TSGs produce proteins that inhibit cell division
  • If altered the proteins may be produced leading to uncontrolled cell division leading to malignant tumour
  • Equally mutation could cause proto oncogene to become an oncogene
  • This causes a gene to become overactive and stimulates cells to divide uncontrollably
•  Explain why fragments of DNA from cancer cells may be present in blood plasma 

  cancer cells die / break open releasing DNA
•   Explain why the nucleic acid on the test strip will only bind to altered DNA

  normal DNA and changed DNA have different sequences

  DNA only binds to complementary sequence
•  Explain why cancer is more likely to be treated successfully if the disease is detected at a very early stage.

  less tumours so fewer locations to treat & less cell damage
•  Explain how examining mRNA (line 7) enables scientists to discover whether cancer is present.

  mRNA base sequence has changedDNA structure is different / has mutatedcancer gene active / tumour suppressor gene inactive
• Patients are tested for antibodies against Zevalin before treatment for their cancer.Suggest why.

   existing antibodies would destroy the Zevalin before it became bound to cancerous B cells, thus making the treatment ineffective.
• What is an antigen?

  protein that causes an immune response
• Describe how alterations to tumour suppressor genes can lead to the development of tumours.

  increased methylation or mutation causes TSG amino acid sequence to be altered

  This means that TSGs are not expressed so protein inhibiting cell division is not produced

  This leads to uncontrolled cell division
•  Explain how increased methylation could lead to cancer.

  Methyl groups added to a tumour suppressor gene

  The transcription of tumour suppressor genes is inhibited meaning protein inhibiting cell division is not produced

   Leading to uncontrolled cell division.
• MM is caused by a faulty receptor protein in cell-surface membranes.Cells in MM tumours can be destroyed by the immune system.

  Suggest why they can be destroyed by the immune system.

   Faulty protein recognised as an antigen / as a foreign protein

  2.      T cells will bind to faulty protein

  3.   T cells will stimulate clonal selection of B cells

  4.      Resulting in release of antibodies against faulty protein.
• features of cancer cells

  • Express different antigens on their cell membrane
  • Larger, darker nuclei
  • Divide by mitosis more frequently
  • Irregular shape
  • Don’t produce all the proteins that a cell needs to function properly
  • Don’t respond to growth-regulating processes