8A 2. cancer Flashcards
uncontrolled cell growth can be caused by
mutations in genes
mutations that occur in individual cells after fertilisation (e.g. in adulthood) are called
acquired mutations
an acquired mutation in genes that control rate of cell division (by mitosis) can cause
uncontrolled cell division
what results from uncontrollably dividing cells
a tumour (a mass of abnormal cells)
tumours that invade and destroy surrounding tissue are called
cancers
the two types of gene that control cell division
tumour suppressor genes and proto-oncogenes
what do tumour suppressor genes do when functioning normally
slow cell division by producing proteins that stop cells dividing or cause them to self-destruct (apoptosis)
what happens if a mutation occurs in a tumour suppressor gene
tumour supressor gene inactivated
protein isn’t produced
cells divide uncontrollably (rate of division increases)
resulting in a tumour
what to proto-onco genes do when functioning normally
stimulate cell division by producing proteins that make cells divide
what happens if a mutation occurs in a proto-oncogene
gene can become overactive
cells divide uncontrollably (rate of division increases)
resulting in a tumour
what is a mutated proto-oncogene called
an oncogene
what are the two types of cancer
benign
malignant
features of malignant tumours
grow rapidly, invade and destroy surrounding tissue.
how do malignant tumours spread
cells break off tumours and spread to other parts of the body in the blood stream or lymphatic system.
are malignant tumours cancers?
yes
features of benign tumours
grow slower
covered in fibrous tissue that stops cells invading other tissues
are benign tumours cancers?
no but can become malignant
do benign tumours cause harm?
often harmless HOWEVER can cause blockages and put pressure on organs.
6 ways in which tumour cells differ from normal cells
- irregular shape
- nucleus larger and darker (sometimes ore than 1)
- don’t produce all proteins needed to function correctly
- different antigens on surface
- don’t respond to growth regulating processes
- divide by mitosis more frequently
what does methylation mean
adding a methyl -CH3 group onto something
how is methylation of DNA an important method of regulating gene expression
controls wether or not a gene is transcribed (copied into mRNA) and translated (turned into protein)
hypermethylation is when
methylation happens too much
hypomethylation is when
methylation happens too little
abnormal methylation of certain cancer related genes can cause
growth of tumours
what happens when tumour suppressor genes are hypermethylated
genes are not transcribed
proteins produced to slow cell division not made
cells divide uncontrollably by mitosis and tumours develop
what happens when proto-oncogenes are hypomethylated
causes them to act as oncogenes
increased production of proteins that encourage cell division
cells divide uncontrollably by mitosis and tumours develop
what is increased exposure to oestrogen is thought to do
increase womans risk of developing breast cancer
2 THEORIES of how oestrogen can contribute to the development of some breast cancers
- Oestrogen can stimulate certain breast cells to divide and replicate.
more cell division = increased chance of mutations occurring = increased chance of cells becoming cancerous
if cells become cancerous, rapid replication could be further assisted by oestrogen, helping tumours to form quickly. - Oestrogen can introduce mutations directly into DNA of certain breast cells = increased chance of cells becoming cancerous
