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Biology AQA A Level > Topic 8 Exam Questions: The Control Of Gene Expression > Flashcards

Topic 8 Exam Questions: The Control Of Gene Expression Flashcards

1
Q

8.1 - Gene Mutations

Explain how a single base substitution causes a change in the structure of this polypeptide (not transcription or translation) (3)

A
  1. Change in (sequence of) amino acids/primary structure
  2. Change in hydrogen/ionic/disulfide bonds
  3. Alters tertiary structure
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2
Q

8.1 - Gene Mutations

What is a substitution mutation? (1)

A

Replacement of a base by a different base (in DNA)

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3
Q

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)

A
  1. (EGCG) bind to active site of DNMT
  2. (DNMT) can’t methylate (promotor region of tumour suppressor gene)
  3. Transcriptional factor can bind (to promotor region)
  4. RNA polymerase (stimulated/activated)
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4
Q

8.2 - Cancer

Describe how alterations to tumour suppressor genes can lead to development of tumours. (3)

A
  1. (Increased) methylation (of tumour suppressor genes)
  2. Mutation (in tumour suppressor genes)
  3. Tumour suppressor genes are not transcribed/expressed OR amino acids sequence/primary structure altered
  4. (Results in) rapid/uncontrolled cell division
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5
Q

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)

A
  1. ATM will not bind to DNA
  2. DNA not repaired
  3. Cell division continues/tumour forms
  4. Tumour suppressor (gene) not effective/activated
  5. May have no effect in diploid/heterozygous (organism)
  6. (Which) still has a functional ATM/ATM gene
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6
Q

8.2 - Cancer

Define what is meant by epigenetics. (2)

A
  1. Heritable changes in gene function
  2. Without changes to the base sequence of DNA
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7
Q

8.2 - Cancer

Explain how increased methylation could lead to cancer. (3)

A
  1. Methyl groups (could be) added to (both copies of) a tumour suppressor gene
  2. The transcription of tumour suppressor genes is inhibited
  3. Leading to uncontrolled cell division
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8
Q

8.2 - Cancer

Give one way in which benign tumour differ from malignant tumours. (1)

A

Cells of benign tumour can’t spread to other parts of the body/metastasise OR
cells of benign tumours can’t invade neighbouring tissues

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9
Q

8.2 - Cancer

Explain how methylation of tumour suppressor genes can lead to cancer. (3)

A
  1. Methylation prevents transcription of gene
  2. Protein not produced that prevents cell division/causes cell death/apoptosis
  3. No control of mitosis
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10
Q

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)

A
  1. Faulty protein recognised as an antigen
  2. T cells will bind to faulty protein/to (this) ‘foreign’ protein
  3. (Sensitised) T cells will stimulate clonal selection of B cells
  4. (Resulting in) release of antibodies against faulty protein.
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11
Q

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)

A

(Cell/memebrane has a) phospholipid bilayer
OR
no channel/carrier protein (for uptake)
OR
No need for channel/carrier protein (for uptake)

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12
Q

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)

A
  1. Lipid soluble
  2. (Diffuse through) phospholipid (bilayer)
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13
Q

8.2 Epigenetics and RNA interference

Suggest and explain why testosterone binds to specific AR (androgen receptor). (2)

A
  1. Has a (specific) tertiary structure/shape
  2. (Structure are) complementary
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14
Q

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)

A
  1. (Receptor is) a transcription factor
  2. Binds to DNA/ promoter
  3. (Stimulates) RNA polymerase
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15
Q

8.2 Epigenetics and RNA interference

Suggest and explain one way epigenetics may affect the age when symptoms of Huntington’s disease start. (2)

A
  1. (Increased) methylation of DNA/gene/allele
  2. Inhibits/prevents transcription
    OR 3. Decreased methylation of DNA/gene/allele
  3. Stimulates/allows transcription
    OR 5. Decreased acetylation of histones
  4. Inhibits transcription
    OR 7. Increased acetylation of histones
  5. Stimulates /allows transcription
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16
Q

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)

A
  1. Cell membranes made from phospholipid
  2. (Detergent) dissolves membranes/phospholipid (bilayer)
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17
Q

8.2 Epigenetics and RNA interference

Explain how ultracentrifugatuon separated protein CENP-W from other molecules. (2)

A
  1. Spin (liquid/supernatant) at (very) high speed
  2. Molecules/ CENP-W separates depending on (molecular) mass/size/density
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18
Q

8.2 Epigenetics and RNA interference

Explain how increased methylation could lead to cancer. (3)

A
  1. Methyl groups (could be) added to (both copies of) a tumour suppressor gene
  2. The transcription of tumour suppressor genes is inhibited
  3. Leading to uncontrolled cell division
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19
Q

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)

A
  1. Greater blood supply (to damaged areas)
  2. Bringing more oxygen / glucose for respiration
  3. Brings more amino acids for protein synthesis
  4. For cell repair/mitosis/division
20
Q

8.3 - Genome Projects

Suggest and explain how the viruses became able to infect other species of frog. (2)

A
  1. Mutation in viral DNA/RNA/genome/genetic material
  2. Altered (tertiary structure of the) viral attachment protein
  3. Allows it/attachment protein/virus to bind (to receptors of other species
21
Q

8.3 - Genome Projects

Name two techniques the scientists may have used when analysing viral DNA to determine the viruses were closely related (1)

A
  1. The polymerase chain reaction
    2 . Genetic/DNA fingerprinting
    3 (Gel) electrophoresis
  2. DNA/genome sequencing
22
Q

8.3 - Genome Projects

Determining the genome of a virus could allow scientists to develop a vaccine. Explain how. (2)

A
  1. Scientists could identify proteins (that derive from the genetic code)
    OR could identify the proteome
  2. Could then identify potential antigens (to use in the vaccine)
23
Q

8.3 - Genome Projects

Describe how the B lymphocytes would respond to vaccination against Ranavirus. (3)

A
  1. B cell (antibody) binds to (viral) specific/complementary receptor/antigen
  2. B cell clones OR B cell divides by mitosis
  3. Plasma cells release/produce (monoclonal) antibodies (against the virus)
  4. (B/plasma cells produce/develop) memory cells
24
Q

8.3 - Genome Projects

What is meant by a genome? (1)

A

(All) the DNA in a cell/organism

25
Q

8.3 - Genome Projects

Explain why the antibody binds to the transcription factor. (2)

A
  1. (Transcriptional factor/antibody) has a specific tertiary structure/shape
  2. Complementary (shape/structure)
26
Q

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)

A
  1. Extract DNA and add restriction enzymes
  2. Separate fragments using electrophoresis
  3. (Treat DNA to) form single strands
    OR (treat DNA to) expose bases
  4. The probe will bind to/hybridise/base pair with the SUT1/ gene
  5. Is autoradiography/ X ray film (to show the bound probe)
27
Q

8.4 - DNA probe and Gel Electrophoresis

What is a DNA probe? (2)

A
  1. (Short) Single strand of DNA
  2. Bases complementary (with DNA/allele/gene)
28
Q

8.4 - DNA probe and Gel Electrophoresis

Describe how the DNA is broken down into smaller fragments (2)

A
  1. Restriction enzyme
  2. (Cuts DNA at specific) base sequence
    OR (breaks) phosphodiester bonds
    OR (cuts DNA) at recognition /restriction site
29
Q

8.4 - DNA probe and Gel Electrophoresis

Explain why the DNA is treated to make it single stranded. (1)

A

(So DNA) probe binds/attaches/anneals

30
Q

8.4 - DNA probe and Gel Electrophoresis

What is meant by a non-coding base sequence? (1)

A

Doesn’t code for amino acid/tRNA/rRNA

31
Q

8.4 - DNA probe and Gel Electrophoresis

Name the process by which a base in base sequence is lost (1)

A

Deletion mutation

32
Q

8.4 - DNA probe and Gel Electrophoresis

Give the name of the method they used to clone the DNA in vitro (1)

A

(The) polymerase chain reaction

33
Q

8.4 - DNA probe and Gel Electrophoresis

Explain how DNA probes are used to produce results (3)

A
  1. Probes are single stranded /have a specific base sequence
  2. Complementary base sequence on (specific) spacer *spacer is non-coding base sequences
    OR
  3. Complementary/specific to (particular) spacer
  4. Binds (to single stranded spacer) and glows /produces light/fluoresce
34
Q

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)

A
  1. To see if strain is resistant to any antibiotics
  2. Soo can prescribe effective /right antibiotic
    OR
  3. See whether (any) vaccine works against this strain/see which vaccine to use/to produce specific vaccine
  4. (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
  5. Allowing control of spread of disease/vaccinate/treat contacts (of people with same strain) before they get TB
35
Q

8.4 - Recombinant DNA

describe how enzymes could be used to insert a gene into a plasmid (2)

A
  1. Restriction enzymes cuts plasmid OR restriction enzyme produces ‘sticky ends’
  2. Ligase joins gene/DNA and plasmid OR ligase joins ‘sticky ends’
36
Q

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)

A
  1. Cell division has occurred (before gene added)
  2. (Cells producing ) gametes don’t receive the gene
37
Q

8.4 - Recombinant DNA

Describe the roles of two named types of enzymes used to insert DNA fragments into plasmids. (2)

A
  1. Restriction (enzyme) to cut plasmid/vector
  2. Ligase joins gene/DNA to plasmid/vector
38
Q

8.4 - Recombinant DNA

Explain the role of reverse transcriptase (1)

A

Produces (c)DNA using (m)RNA

39
Q

8.4 - Recombinant DNA

Explain the role of DNA polymerase (1)

A

Joins NUCLEOTIDES to produce (complementary strands/of) DNA

40
Q

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)

A
  1. To remove any DNA present
  2. As this DNA would be amplified/ replicated
41
Q

8.4 - Recombinant DNA

Suggest one reason why DNA replication stops in the polymerase chain reaction. (1)

A

Limited number of primers/nucleotides

42
Q

8.4 - Recombinant DNA

The scientists used a variety of primers to detect the presence of different RNA in viruses. Explain why. (2)

A
  1. Base sequences differ
  2. (Different) COMPLEMENTARY primers required
43
Q

8.4 - Recombinant DNA

Describe how a geneticist would attempt to insert copies of a gene into plasmids (3)

A
  1. Cut plasmid with a restriction endonuclease
  2. (So that) both have complementary /sticky ends
  3. (Mix together) and add ligase to join the complementary/sticky ends
44
Q

8.4 - Recombinant DNA

Suggest why the scientists used a marker gene and why they used the gene. (2)

A
  1. Not all cells would have taken up the plasmid successfully
  2. Cells that took up the gene will glow
45
Q

8.4 - Recombinant DNA

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

A
  1. (Requires DNA fragment) DNA polymerase, (DNA) nucleotides and primers
  2. Heat to 95°C to break hydrogen bonds (and separate strands)
  3. Reduce temperature soo primers bind to DNA/strands
  4. Increase temperature, DNA polymerase joins nucleotides (and repeat method)

Biology AQA A Level (4 decks)

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