biology-genes,mutations and cancer

• do all cells produce all the proteins in the body

  no some cells only produce specific proteins such as the pancreatic beta cells only producing insulin

  or the myosin found in skeletal muscle.
• what are transcription factors

  -they control the transcription of genes

  -they are proteins
• how do transcription factors work

  -they move from the cytoplasm to the nucleus

  -where they bind to specific DNA sites near the start of the target gene

  -the expression of the gene is controlled by controlling the rate of transcription

  -2 types of transcription factors: activators or repressors
• how does oestrogen initiate transcription of target genes

  because oestrogen is a lipid based hormone it can bind to the transcription factor forming an oestrogen-oestrogen receptor complex that moves from the cytoplasm to the nucleus and binds to the target DNA and acts as an activator.
• how do epigenetics contol gene expression

  -the attachment of certain chemical groups to DNA can switch the gene on or off

  -methalyation binds to DNA causing the transcription factors binging points to be inhibited preventing the transcription factor from binding.
• what are the three main types of gene mutation

  addition

  substitution (nonsense/missense)

  deletion
• give some examples of mutagenic agents that can increase the rate of mutation

  high energy ionising radiation such as x-rays or ultraviolet light

  -these ionise DNA bases so they dont form the correct base pairs during replication
• what are some chemical mutagentic agents that can cause cancer and also treat cancer.

  -base analogues: these substitiute for a base changing the base sequence in the new DNA strand.

  -alkylating agents: add an alkylating group to guanine changing ist structure so it pairs with thymine instead
• what is benzo(a)pyrene 


  -a polycyclic aromatic hydrocarbon

  -found in cigarette smoke

  -can bind to DNA and cause guanine to bind to thymine
• how are normal cells different frm cancer cells

  -they require growth factors to divide

  -they stop dividing when they come into contact with another cell

  -they undergo apoptosis(controlled cell death)

  -when the DNA i damaged the cell stops dividing and dies.
• what is a benign tumour 


  a tumour that is slow growing harmless and doesnt invade surrounding tissues
• what is a malignant tumour 


  they grow rapidly and invade and destroy the surrounding tissues

  they can also spread to other areas of the body.
• what are tumour suppressor genes

  • Encode proteins that inhibit cell division when activated by stop signals such as damaged DNA

  • Stop cell cycle at checkpoints

  • mutated tumour suppressor genes stop making the protein so allow cells to continue to divide

  • Both copies of the gene need to be mutated to allow uncontrolled cell division
• what does p53 do

  p53, a transcription factor that binds to DNA, activating transcription of a protein called p21.

  • p21 blocks progression through G1 which allows time for the cell to repair the DNA before it is replicated.

  • If the DNA damage is so extensive that it cannot be repaired,

  p53 triggers the cell to commit suicide.

  • The most common mutation leading to cancer is in the gene that makes p53.
• what are proto-oncogenes 


  Encode proteins that stimulate cell division when

  activated by protein growth factors such as hormones

  • This activated protein allows cells to divide by passing

  checkpoints

  • A mutation in a proto-oncogene creates an oncogene -

  makes too much active protein regardless of signal

  • A mutation in one copy is enough to cause growth.
• what is the braca 1/2gene

  a tumour suppressor gene that has mutated and can cause breast cancer.
• what are some ways to treat cancer

  1.Surgery: Often called resection.

  Essentially, cut the neoplastic tissue out of the body.

  2. Radiotherapy:Also called radiation therapy.

  Focus bursts of ionising radiation on neoplastic cells, damaging their DNA and causing cell death.

  3. Chemotherapy

  The use of pharmaceuticals as an anti-cancer strategy

  (often DNA damaging agents).
• how does acelyation affect gene transcription


  causes the DNA to be wound around the histone less tightly allowing the transcription factors to bind to the DNA.allowing the gene to be switched on.