Topic 8 Exam Questions: The Control Of Gene Expression Flashcards
8.1 - Gene Mutations
Explain how a single base substitution causes a change in the structure of this polypeptide (not transcription or translation) (3)
- Change in (sequence of) amino acids/primary structure
- Change in hydrogen/ionic/disulfide bonds
- Alters tertiary structure
8.1 - Gene Mutations
What is a substitution mutation? (1)
Replacement of a base by a different base (in DNA)
8.2 - Cancer
Throat cancer is caused by increased methylation of promoter region of tumour suppressor gene. Methylation is caused by enzyme DNMT. EGCG is a competitive inhibitor of DNMT and allows daughter cells to produce mRNA from tumour suppressor gene. Suggest how EGCG allows the production of mRNA in daughter cells. (3)
- (EGCG) bind to active site of DNMT
- (DNMT) can’t methylate (promotor region of tumour suppressor gene)
- Transcriptional factor can bind (to promotor region)
- RNA polymerase (stimulated/activated)
8.2 - Cancer
Describe how alterations to tumour suppressor genes can lead to development of tumours. (3)
- (Increased) methylation (of tumour suppressor genes)
- Mutation (in tumour suppressor genes)
- Tumour suppressor genes are not transcribed/expressed OR amino acids sequence/primary structure altered
- (Results in) rapid/uncontrolled cell division
8.2 - Cancer
ATM binds to stop cell division until DNA is repaired. A mutation could result in a person having non-functional forms of gene that produces ATM. What can you predict about the possible effects of having non-functional form if ATM? (3)
- ATM will not bind to DNA
- DNA not repaired
- Cell division continues/tumour forms
- Tumour suppressor (gene) not effective/activated
- May have no effect in diploid/heterozygous (organism)
- (Which) still has a functional ATM/ATM gene
8.2 - Cancer
Define what is meant by epigenetics. (2)
- Heritable changes in gene function
- Without changes to the base sequence of DNA
8.2 - Cancer
Explain how increased methylation could lead to cancer. (3)
- Methyl groups (could be) added to (both copies of) a tumour suppressor gene
- The transcription of tumour suppressor genes is inhibited
- Leading to uncontrolled cell division
8.2 - Cancer
Give one way in which benign tumour differ from malignant tumours. (1)
Cells of benign tumour can’t spread to other parts of the body/metastasise OR
cells of benign tumours can’t invade neighbouring tissues
8.2 - Cancer
Explain how methylation of tumour suppressor genes can lead to cancer. (3)
- Methylation prevents transcription of gene
- Protein not produced that prevents cell division/causes cell death/apoptosis
- No control of mitosis
8.2 - Cancer
MM is caused by a faulty receptor protein in cell-surface membranes. Cells in MM tumours can be destroyed by the immune system. Suggest why they can be destroyed by the immune system. (3)
- Faulty protein recognised as an antigen
- T cells will bind to faulty protein/to (this) ‘foreign’ protein
- (Sensitised) T cells will stimulate clonal selection of B cells
- (Resulting in) release of antibodies against faulty protein.
8.2 Epigenetics and RNA interference
One method of transferring RNAi molecules into cells involves combining these molecules with a lipid. Suggest why this increases uptake of RNAi molecules into cells (1)
(Cell/memebrane has a) phospholipid bilayer
OR
no channel/carrier protein (for uptake)
OR
No need for channel/carrier protein (for uptake)
8.2 Epigenetics and RNA interference
Testosterone is asteroid hormone. Steroid hormones are hydrophobic. Explain why steroid hormones can rapidly enter a cell by passing through its cell-surface membrane. (2)
- Lipid soluble
- (Diffuse through) phospholipid (bilayer)
8.2 Epigenetics and RNA interference
Suggest and explain why testosterone binds to specific AR (androgen receptor). (2)
- Has a (specific) tertiary structure/shape
- (Structure are) complementary
8.2 Epigenetics and RNA interference
The binding of testosterone to a specific receptor changes the shape of the receptor. The receptor now enters the nucleus and stimulates gene expression. Suggest how the receptor stimulates gene expression. (2)
- (Receptor is) a transcription factor
- Binds to DNA/ promoter
- (Stimulates) RNA polymerase
8.2 Epigenetics and RNA interference
Suggest and explain one way epigenetics may affect the age when symptoms of Huntington’s disease start. (2)
- (Increased) methylation of DNA/gene/allele
- Inhibits/prevents transcription
OR 3. Decreased methylation of DNA/gene/allele - Stimulates/allows transcription
OR 5. Decreased acetylation of histones - Inhibits transcription
OR 7. Increased acetylation of histones - Stimulates /allows transcription
8.2 Epigenetics and RNA interference
Scientists began by lysing cells and organelles using detergent that dissolves lipids in water to investigate the role of a protein called CENP-W in mitosis. Suggest how the detergent releases CENP-W from cells. (2)
- Cell membranes made from phospholipid
- (Detergent) dissolves membranes/phospholipid (bilayer)
8.2 Epigenetics and RNA interference
Explain how ultracentrifugatuon separated protein CENP-W from other molecules. (2)
- Spin (liquid/supernatant) at (very) high speed
- Molecules/ CENP-W separates depending on (molecular) mass/size/density
8.2 Epigenetics and RNA interference
Explain how increased methylation could lead to cancer. (3)
- Methyl groups (could be) added to (both copies of) a tumour suppressor gene
- The transcription of tumour suppressor genes is inhibited
- Leading to uncontrolled cell division
8.2 - Stem cells
Suggest how the growth of new blood vessels into damaged heart tissues could increase the rate of repair of tissues. (3)
- Greater blood supply (to damaged areas)
- Bringing more oxygen / glucose for respiration
- Brings more amino acids for protein synthesis
- For cell repair/mitosis/division
8.3 - Genome Projects
Suggest and explain how the viruses became able to infect other species of frog. (2)
- Mutation in viral DNA/RNA/genome/genetic material
- Altered (tertiary structure of the) viral attachment protein
- Allows it/attachment protein/virus to bind (to receptors of other species
8.3 - Genome Projects
Name two techniques the scientists may have used when analysing viral DNA to determine the viruses were closely related (1)
- The polymerase chain reaction
2 . Genetic/DNA fingerprinting
3 (Gel) electrophoresis - DNA/genome sequencing
8.3 - Genome Projects
Determining the genome of a virus could allow scientists to develop a vaccine. Explain how. (2)
- Scientists could identify proteins (that derive from the genetic code)
OR could identify the proteome - Could then identify potential antigens (to use in the vaccine)
8.3 - Genome Projects
Describe how the B lymphocytes would respond to vaccination against Ranavirus. (3)
- B cell (antibody) binds to (viral) specific/complementary receptor/antigen
- B cell clones OR B cell divides by mitosis
- Plasma cells release/produce (monoclonal) antibodies (against the virus)
- (B/plasma cells produce/develop) memory cells
8.3 - Genome Projects
What is meant by a genome? (1)
(All) the DNA in a cell/organism
8.3 - Genome Projects
Explain why the antibody binds to the transcription factor. (2)
- (Transcriptional factor/antibody) has a specific tertiary structure/shape
- Complementary (shape/structure)
8.4 - DNA probe and Gel Electrophoresis
The scientists used a radioactively labelled DNA probe to show that the cells of tobacco leaves contained the SUT1 (sucrose co-transport protein). Describe how they would do this. (4)
- Extract DNA and add restriction enzymes
- Separate fragments using electrophoresis
- (Treat DNA to) form single strands
OR (treat DNA to) expose bases - The probe will bind to/hybridise/base pair with the SUT1/ gene
- Is autoradiography/ X ray film (to show the bound probe)
8.4 - DNA probe and Gel Electrophoresis
What is a DNA probe? (2)
- (Short) Single strand of DNA
- Bases complementary (with DNA/allele/gene)
8.4 - DNA probe and Gel Electrophoresis
Describe how the DNA is broken down into smaller fragments (2)
- Restriction enzyme
- (Cuts DNA at specific) base sequence
OR (breaks) phosphodiester bonds
OR (cuts DNA) at recognition /restriction site
8.4 - DNA probe and Gel Electrophoresis
Explain why the DNA is treated to make it single stranded. (1)
(So DNA) probe binds/attaches/anneals
8.4 - DNA probe and Gel Electrophoresis
What is meant by a non-coding base sequence? (1)
Doesn’t code for amino acid/tRNA/rRNA
8.4 - DNA probe and Gel Electrophoresis
Name the process by which a base in base sequence is lost (1)
Deletion mutation
8.4 - DNA probe and Gel Electrophoresis
Give the name of the method they used to clone the DNA in vitro (1)
(The) polymerase chain reaction
8.4 - DNA probe and Gel Electrophoresis
Explain how DNA probes are used to produce results (3)
- Probes are single stranded /have a specific base sequence
- Complementary base sequence on (specific) spacer *spacer is non-coding base sequences
OR - Complementary/specific to (particular) spacer
- Binds (to single stranded spacer) and glows /produces light/fluoresce
8.4 - DNA probe and Gel Electrophoresis
Suggest and explain why it is important to be able to identify the specific strain of M.tuberculosis infect a patient. (2)
- To see if strain is resistant to any antibiotics
- Soo can prescribe effective /right antibiotic
OR - See whether (any) vaccine works against this strain/see which vaccine to use/to produce specific vaccine
- (So) can vaccinate potential contacts/to stop spread
OR 5. Can test other people to see if they have the same strain/trace where people caught TB - Allowing control of spread of disease/vaccinate/treat contacts (of people with same strain) before they get TB
8.4 - Recombinant DNA
describe how enzymes could be used to insert a gene into a plasmid (2)
- Restriction enzymes cuts plasmid OR restriction enzyme produces ‘sticky ends’
- Ligase joins gene/DNA and plasmid OR ligase joins ‘sticky ends’
8.4 - Recombinant DNA
Suggest and explain how a delayed insertion of a gene could produce offspring of a fish without the desired characteristic(2)
- Cell division has occurred (before gene added)
- (Cells producing ) gametes don’t receive the gene
8.4 - Recombinant DNA
Describe the roles of two named types of enzymes used to insert DNA fragments into plasmids. (2)
- Restriction (enzyme) to cut plasmid/vector
- Ligase joins gene/DNA to plasmid/vector
8.4 - Recombinant DNA
Explain the role of reverse transcriptase (1)
Produces (c)DNA using (m)RNA
8.4 - Recombinant DNA
Explain the role of DNA polymerase (1)
Joins NUCLEOTIDES to produce (complementary strands/of) DNA
8.4 - Recombinant DNA
Any DNA in the sample is hydrolysed by enzymes before the sample is added to the reaction mixture. Explain why. (2)
- To remove any DNA present
- As this DNA would be amplified/ replicated
8.4 - Recombinant DNA
Suggest one reason why DNA replication stops in the polymerase chain reaction. (1)
Limited number of primers/nucleotides
8.4 - Recombinant DNA
The scientists used a variety of primers to detect the presence of different RNA in viruses. Explain why. (2)
- Base sequences differ
- (Different) COMPLEMENTARY primers required
8.4 - Recombinant DNA
Describe how a geneticist would attempt to insert copies of a gene into plasmids (3)
- Cut plasmid with a restriction endonuclease
- (So that) both have complementary /sticky ends
- (Mix together) and add ligase to join the complementary/sticky ends
8.4 - Recombinant DNA
Suggest why the scientists used a marker gene and why they used the gene. (2)
- Not all cells would have taken up the plasmid successfully
- Cells that took up the gene will glow
8.4 - Recombinant DNA
Describe and explain how the polymerase chain reaction (PCR) is used to amplify a DNA fragment. (4)
- (Requires DNA fragment) DNA polymerase, (DNA) nucleotides and primers
- Heat to 95°C to break hydrogen bonds (and separate strands)
- Reduce temperature soo primers bind to DNA/strands
- Increase temperature, DNA polymerase joins nucleotides (and repeat method)
