Unit 8 Flashcards
How do alterations to tumour suppressor genes lead to cancer. (4)
- Increased methylation (of tumour suppressor genes);
- Mutation (in tumour suppressor genes);
- Tumour suppressor genes are not transcribed/expressed/mRNA not produced OR Amino acid sequenceor different amino acid/primary or tertiary structure altered;
- (Results in) rapid/uncontrollable cell division/cell division not regulated;
What is a Transcription Factor? (3)
- (Protein/molecule) that moves from cytoplasm to DNA;
- (TF) binds to specific gene/genes/ to specific part of/site on DNA/ binds to promoter/RNA polymerase; 3. Leads to/blocks (pre)mRNA production / allows/blocks binding of RNA polymerase
How does oestrogen stimulate Transcription? (6)
- Oestrogen diffuses through the cell membrane;
- attaches to receptor;
- receptor changes shape;
- receptor leaves protein complex which inhibited its action; 5. oestrogen receptor binds to promoter region;
- enables RNA polymerase to transcribe target gene
Describe RNA Interference. (3)
- MicroRNA/siRNA binds to cell’s mRNA by specific base pairing; 2. (So) prevents mRNA being read by ribosomes;
- prevents translation/production of proteins
Define Epigenetics. (2)
- Heritable changes in gene function;
- Without changes to the base sequence of DNA;
Describe how methylation leads to cancer. (3)
- Methyl groups (could be) added to (both copies of) a tumour suppressor gene; 2. The transcription of tumour suppressor genes is inhibited;
- Leading to uncontrolled cell division/mitosis;
Describe the method of in-vivo cloning with the use of an antibiotic resistant marker gene (8)
- isolate wanted gene / DNA from another organism / mRNA from cell / organism;
- using restriction endonuclease / restriction enzyme / reverse transcriptase to get DNA and
- produce sticky ends;
- use ligase to join wanted gene to plasmid;
- include marker gene e.g. antibiotic resistance;
- add plasmid to bacteria to grow (colonies)then (replica) plate onto medium where the marker gene is expressed; 7. not killed have antibiotic resistance gene and (probably) the wanted gene
Describe the process of in- vitro cloning using PCR (9)
- DNA heated to 90 to 95°C;
- strands separate;
- cooled / to temperature below 70°C
- primers bind; (primers identify the DNA sequence to be amplified) 5. nucleotides attach;
- by complementary base pairing;
- temperature 70 - 75°C;
- DNA polymerase joins nucleotides together;
- cycle repeated;
Describe the use of DNA probes in gene testing. (4)
- probe will attach ( e.g. to allele);
- attaches to one DNA strand;
- as a result of complementary base pairing;
- radioactivity detected on film / X-ray / by autoradiography;
Outline the process of genetic fingerprinting (10)
- DNA extracted from sample;
- DNA cut into segments using restriction endonucleases;
- Must leave VNTR / required core sequences intact;
- DNA fragments separated using electrophoresis;
- detail of process e.g. mixture put into wells on gel and electric current passed through; 6. immerse gel in alkaline solution / two strands of DNA separated;
- Southern blotting / over with nylon / absorbent paper (to absorb DNA)
- DNA fixed to nylon / membrane using UV light;
- radioactive marker / probe added complementary to VNTR;
- (areas with probe) identified using X-ray film
How does decrease acetylation affect transcription?
Inhibits transcription
Histones become more tightly coiled around DNA
So transcription factors can’t bind
What is a tumour suppressor gene?
A gene which codes for proteins which slow down cell division (control mitosis) and causes cell death if errors are detected.
What is a stem cell?
An undifferentiated cell which can continually divide to become specialised.
describe how RNAi can inhibit translation
An enzyme can cut the mRNA into siRNA.
One strand of the siRNA then combines with another enzyme.
This siRNA- enzyme complex will bind via complementary base pairing to another mRNA molecule.
Once bound, the enzyme with cut up the mRNA so it cannot be translated.
