cancer genes and methylation

Question 1

chromatin

Answer 1

DNA-histone complex

Question 2

where association of histones w DNA = weak …

Answer 2

DNA-histone complex less condensed

accessible to transcription factors which initiate production of mRNA

Question 3

acetylation

Answer 3

process where acetyl group is transferred to a molecule

Question 4

decreasing acetylation of DNA…

Answer 4

• ↑ positive charges on histones
• ↑ attraction to phosphate groups on DNA
• DNA not accessible to transcription factors
• no mRNA
• gene switched off

Question 5

increased methylation of DNA…

Answer 5

• methyl added to cytosine base of DNA
  attracting proteins that condense DNA-histone complex by inducing deactlyation of histones, making DNA inaccessible to transcription factors

Question 6

methylation

Answer 6

addition of methyl group to molecule

Question 7

how can hypERmethylation cause cancer?

Answer 7

hypermethylation of tumour suppressor genes means that genes are not transcribed and proteins slowing cell division aren’t made ∴ uncontrolled cell division and cancer

Question 8

features of benign tumour (5)

Answer 8

• grow to a large size
• slow growing
• nucleus is relatively normal in appearance
• cells are well differentiated
• cells produce adhesion molecules which help them stick together so they remain in the tissues they arise from = primary tumour

Question 9

features of malignant tumour (5)

Answer 9

• grow to a large size
• grow fast
• cell nucleus is larger + darker due to abundance of DNA
• cells become de-differenciated
• cells do not produce adhesion molecules so they spread to other areas of the body (metastasis) = secondary tumours

Question 10

proto-oncogenes function

Answer 10

stimulate cells to divide when growth factors attach to protein receptor on cell surface membrane - this activates the gene that cause DNA to replicate and cell to divide

Question 11

2 reasons gene can be permanent activated if porto-oncogene is mutated into oncogene:

Answer 11

• receptor proteins on cell surface membrane can be permanently activated therefore cell division is switched on even if no growth factor
• oncogene may code for growth factor that is then produced in excessive amounts stimulating excess cell division

Question 12

2 main genes in cancer growth

Answer 12

• oncogenes

- tumour supressor genes