Molecular basis of cancer

Question 1

what does DNA have

Answer 1

bases

Question 2

what do bases fo

Answer 2

code the RNA and protein

this affects the cells

Question 3

changes in DNA sequence…

Answer 3

If you get a change in DNA, can lead to change in mRNA then change in tRNA, then change sequence of protein (change in aa sequence)

Question 4

what can DNA mutations lead to

Answer 4

changes in levels or function of the gene products

Question 5

How is t RNA produced

Answer 5

1) DNA unwinds
2) mRNA produced
3) mRNA translocates into cytoplasm
4) Acts as a template at the ribosome
5) forms a sequence with tRNA

Question 6

types of mutation

Answer 6

point
gene amplification
chromosomal translocations

Question 7

point mutations

Answer 7

single base change

change aa

Question 8

results of point mutations

Answer 8

framshift

• can introduce STOP codon
• change splicing
• silent mutations(no aa change)
• can lose base, moving entire sequence up (change in codon onwards)

Question 9

introduction of STOP codon

Answer 9

leads to a truncated protein, either does not work or has an altered function

Question 10

change splicing

Answer 10

mRNA needs to be spliced to remove introns, mutations in splice sites can either leave introns in or alter the sequence, generally stops production of protein

Question 11

gene amlification

Answer 11

• whole regions of DNA copied more times than they should be
• normally only one gene, when the DNA copies itself can accidently copy the gene several times
• each gene will act normally and express itself, therefore there will be an overexpression
• sends lots of signals to the nucleus

Question 12

chromosomal translocations

Answer 12

• movement of whole chromosomes
• bits of one chromosome can swap with another part
• The pairs of chromosomes should be the same
• swap between chromosome regions can lead to eg a receptor to express at different levels
• affects how cell behaves and divides

Question 13

somatic mutations

Answer 13

occur in non germline tissues
non heritable
can occur anywhere
accumulate mutations in life
- mutations can occur in the wrong part, genome causes worse changes

Question 14

gremlin mutations

Answer 14

present in sperm and egg
heritable
cause cancer family syndrome

Question 15

de novo

Answer 15

can have history of germ mitations

Question 16

characteristics of cancer cells

Answer 16

• excess proliferation without external stimuli
• loss of control mechanisms
• loss of apoptosis
• defects in DNA
• irreversible, limitless change
• acquisition of a blood supply into the tumour– angiogenesis
• invasion of surrounding structures

Question 17

gees involved in cancer

Answer 17

oncogenes
tumour suppressor genes
apoptosis genes
mismatch repair genes

Question 18

oncogenes

Answer 18

• apply the accelerator to cell proliferation
• promote autonomous cell growth and proliferation (no external signal prompts this proliferation in cancer)
• code for growth factors and their receptors signal transducers and cell cycle components
• normal function in controlling cell proliferation and cell division balance (proto oncogenes in normal cells, oncogenes in cancer cells)
• increased expression (activation)or activity in malignancy

Question 19

tumour suppressor genes

Answer 19

• apply brakes to cell proliferation
• code for factors which control the cell cycle, regulate apoptosis, transcription or cell interactions
• normal function in supressing cell proliferation and maintaining tissue integrity
• loss of expression (gene deletion) or function (mutations) in malignancy

Question 20

apoptosis genes

Answer 20

• Genes that regulate normal cell death
  may see
• increased activity of a gene which inhibits apoptosis
• reduced activity of genes which promote apoptosis

Question 21

which gene is overexpressed In lymphomas

Answer 21

BCL2

apoptosis gene

Question 22

mismatch reapir genes

Answer 22

• code for enzymes important for the repair of damaged DNA
• DNA damage common due to environmental carcinogens
• loss of expression (deletion) or function (mutation) in malignancy
• loss of repair mechanisms increases risk of mutations and activations or loss of oncogenes and tumour suppressor genes
• allows mutations to accumulate

Question 23

what is proliferation

Answer 23

several rounds of cell divisio

Question 24

two hit hypothesis

Answer 24

Hit 1
-	inherited loss of gene on one chromosome (germline mutation)
Hit 2
-	sporadic loss on second chromosome
leads to cancer

Question 25

factors in carcinogenesisi

Answer 25

genetic (mutations)
environmental (e.g. UV)
chemcials (e.g. tobacco)
viruses

Question 26

multistage carcinogenesis

Answer 26

Generally takes a lot of hits to allow the development of cancer
- cells will heal themselves generally
- until they cannot heal themselves, continuing to be exposed to factrs
(multiple genetic events from precancerous to cancer)

Question 27

bowel carcinogenesis

Answer 27

normal
hyperplastic
adenoma
carcinoman
metastasis

Question 28

epigenetic

Answer 28

doesnt involve changes to DNA bases but alters DNA

• chemical changes to DNA
• often occur because of environmental factors age ect
• increasingly thought to be important in cancer
• DNA methylation
• changes to histones

Question 29

tumour microenvironment

Answer 29

contribution of other cells surrounding the tumir

all talk to the tumour