CANCER

CANCER

1. Cancer is caused by a mutation that occurs in the gene that aids cell division

   • The mutation may cause a tumour to form.
     • Malignant tumours are cancerous and they can spread.
       • They kill surrounding tissues
     • Benign tumours are not cancerous but can become malignant
     • Tumours look different to normal cells.
       • They have a darker nucleus.
       • They have different antigens on their surface.
       • They divide faster
       • They have an irregular shape.

2. Proto-oncogenes

   • This gene code codes for a protein which stimulates, cell division.
     • If a mutation occurs in this gene, the protein may be produced in excess.
       • This means cells divide uncontrollably, forming a tumour.
         • This s because cell division occurs spontaneously.

3. Tumour suppressor genes.

   • This gene codes for a protein that slows down or stops cell division.
     • It can also cause cells to self-destruct.
     • However, if a mutation occurs, the protein does not get produced.
       • So rate of cell division increases, forming a tumour.

4. Mutagenic agents

   • These are factors which affect the rate of mutation during DNA replication.
   • Chemicals acting as a base can cause substitution of bases.
   • Chemicals can also alter bases by deletion etc.
     • Finally, ionising radiation can change the structure of DNA.

5. Causes of tumour growth

   • Abnormal methylation of DNA
     • This is when a methyl group gets added to DNA changing its structure
       • Hypermethylation is too much
       • Hypomethylation is too little
   • Increased exposure to oestrogen
     • Can stimulate certain breast cells to divide causing breast cancer.
     • Oestrogen also helps malignant tumours to form quickly.
     • Research shows that it can directly cause mutations in certain breast cells.

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