Unit 8

Question 1

How do alterations to tumour suppressor genes lead to cancer. (4)

Answer 1

1. Increased Methylation (of tumour suppressor genes)
2. Mutation
3. Tumour suppressor genes are not transcribed
4. Results in uncontrollable cell division

Question 2

What is a Transcription Factor (3)

Answer 2

1. Protein that moves from cytoplasm to DNA
2. TF binds to specific gene to specific part of the DNA to the promoter
3. Leads to mRNA production

Question 3

How does oestrogen stimulate Transcription? (6)

Answer 3

1. Oestrogen diffuses through the cell membrane
2. Attaches to receptor
3. Receptor changes shape
4. Receptor leaves protein complex which inhibited its action
5. Oestrogen receptor binds to promoter region
6. Enables RNA polymerase to transcribe target gene

Question 4

Describe RNA Interference (3)

Answer 4

1. siRNA binds to cell’s mRNA by specific bas pairing
2. So prevents mRNA being read by ribosomes
3. Prevents translation

Question 5

Define Epigenetics (2)

Answer 5

1. Heritable changes in gene function
2. Without changes to the base sequence of DNA

Question 6

Describe how methylation leads to cancer (3)

Answer 6

1. Methyl groups added to both copies of a tumour suppressor gene
2. The transcription of tumour suppressor genes is inhibited
3. Leading to uncontrolled cell division

Question 7

Describe the method of in-vivo cloning with the use of an antibiotic resistant marker gene (8)

Answer 7

1. Isolate wanted gene from another organism
2. Using restriction endonuclease
3. Produces sticky ends
4. Use ligase to join wanted gene to plasmid
5. Include marker gene
6. Add plasmid to bacteria to grow colonies then replica plate onto the medium where the maker gene is expressed
7. Not killed therefore they have the antibiotic resistance gene and probably the wanted gene

Question 8

Describe the process of in-vitro cloning using PCR (9)

Answer 8

1. DNA heated to 90 to 95
2. Strands separate
3. Cooled to temperature below 70
4. Primers bind
5. Nucleotides attach
6. By complementary base pairing
7. Temperature 70-75
8. DNA polymerase joins nucleotides together
9. Cycle repeated

Question 9

Describe the use of DNA probes in gene testing (4)

Answer 9

1. Probe will attach
2. Attaches to one DNA strand
3. As a result of complementary base pairings
4. Radioactivity detected on film by autoradiography

Question 10

Outline the process of genetic fingerprinting (10)

Answer 10

1. DNA extracted from sample
2. DNA cut into segments using restriction endonucleases
3. Must leave VNTR
4. DNA fragments separated using electrophoresis
5. Detail of process e.g. Mixture put into wells on gel and electric current passed through
6. Immerse gel in alkaline solution
7. Southern blotting with nylon
8. DNA fixed to nylon using UV light
9. Radioactive marker added complementary to VNTR
10. Areas with probe identified using X-ray film

Question 11

Definition of Stem Cells (1)

Answer 11

1. Undifferentiated cells that can continually divide and become specialised

Question 12

Describe what Totipotent stem cells are (2)

Answer 12

1. Stem cells that can divide and produce any type of body cell.
2. Found only in a limited time in early mammalian embryos

Question 13

Describe what Pluripotent Cells are (2)

Answer 13

1. Can become almost any type of cell
2. Found in embryos
3. Used in research to treat human disorders, such as Parkinson’s

Question 14

How are Multipotent and Unipotent cells similar but also different? (3)

Answer 14

1. Both Stem Cells are found in mature mammals and can divide to form a limited number of different cell types.
2. Multipotent cells, located in bone marrow, can differentiate into a limited number of cells
3. Unipotent cells can only differentiate into one kind of cell, so skin to skin cell

Question 15

Describe and explain how the polymerase chain reaction (PCR) is used to amplify a DNA fragment (4)

Answer 15

1. Requires DNA polymerase, DNA nucleotides and primers
2. Heat to 95C to break hydrogen bonds
3. Reduce temperature so primers bind to DNA
4. Increase temperature, DNA polymerase joins nucleotides