Control of Gene Expression

Option 1:

1. Deletion.
2. Means a codon is missing, so an amino acid is missing from the polypeptide.

1. The DNA base sequence being reversed.
2. Causes a change in the primary structure of the protein/ the order of amino acids.
3. This changes the hydrogen bonds/ ionic bonds/ disulfide bridges between the amino acids.
4. Changing the tertiary structure.

1. An undifferentiated cell.
2. That can divide an unlimited number of times.

1. Stimulating an immune response.
2. Differentiating into the wrong type of cells.
3. Dividing uncontrollably, creating a possibly cancerous tumour.

1. It binds to a receptor in the cytoplasm of target cells, forming an oestrogen-receptor complex.
2. This complex then acts as a transcription factor.
3. By binding to a promoter region on DNA.
4. This causes RNA polymerase to bind to the DNA, increasing transcription.

1. Antisense is complementary to ‘sense’ mRNA.Note: you had to infer this just from the use of the words ‘sense’ and ‘antisense’ btw, so remember this terminology.
2. Antisense mRNA would bind to sense mRNA.
3. Ribosomes would be unable to bind to the sense mRNA.
4. This causes less translation of the sense mRNA and less production of the SUT1 protein.

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

1. If methyl groups are added to a tumour suppressor gene.
2. Transcription factors will be unable to bind to the promoter region of the gene.
3. The next point is that RNA polymerase will be prevented from binding to the gene.
4. This means the transcription of tumour suppressor genes would get inhibited, meaning less tumour suppressor proteins would be produced.
5. This leads to uncontrolled cell division.Note: this is a key phrase you want to use in any cancer question.

1. A change in the base sequence of a tumour suppressor gene could cause non-functional tumour suppressor proteins to form.
2. This means they won’t be able to inhibit the mitosis of cells.
3. This leads to uncontrolled cell division.

1. The drugs could increase methylation of oncogenes.
2. The drugs could decrease methylation of tumour suppressor genes.
3. The drugs could decrease acetylation of the histones of oncogenes.
4. The drugs could increase acetylation of the histones of tumour suppressor genesNote: make sure you always talk about the acetylation of ‘histones’

1. Computerised DNA sequencing.
2. Computerised DNA fingerprinting.
3. PCR amplifies DNA.
4. Gel electrophoresis can separate DNA fragments.
5. DNA probes can be used to identify alleles.

1. The presence of non-coding DNA.
2. Regulatory genesNote: in case you need a third, you may be able to mention post-translational modification of proteins.

1. Determining the genome allows scientists to identify the proteins the pathogen would produce (its proteome).
2. This allows them to then identify potential antigens that can be used in the vaccine.

1. Cut the plasmid with a restriction endonuclease.Note: the same enzyme that’s specific to the gene, of course.
2. This means that the plasmid and gene have complementary sticky ends.
3. Then add ligase to join the sticky ends together.

1. It acts as a marker gene that shows the desired gene has been successfully taken up.Note: use this wording - ‘successfully taken up’. Or say it allows the detection of the ‘genetically modified cells’.
2. As only cells that show fluorescence contain the desired gene.

1. DNA code is universal.
2. The mechanism of transcription is universal.
3. The mechanism of translation is universal.

1. They cannot splice pre-mRNA so they cannot remove introns.
2. They don’t have Golgi apparatus so cannot modify proteins.
3. They may not have the transcriptional factors to carry out the transcription of human DNA into mRNA.

1. It makes it lipid soluble.
2. This means it can diffuse through the phospholipid bilayer.
3. This means a channel/ carrier protein isn’t needed for its uptake.

1. It allows the protein to be harvested without harming the animal.
2. The production of the protein in other cells may cause harm.

1. Cell division has already occurred before the gene is added.
2. This means the gametes do not receive the gene.

1. The DNA is often damaged, interfering with the proteins produced and causing the embryo to die.
2. The embryo’s antigens are often foreign, meaning they get attacked by the immune system of the mother.

1. When injected into the egg, the plasmid will get into most/all the cells of the spider.
2. This means it will get into the cells responsible for producing silk.Note: this shows the importance of making it specific to the question being asked.

1. The strand being inserted is complementary to the strand being translated.Note: It didn’t say this in the question of course - I added it here as a reminder to always say it in any of these DNA technology questions.
2. The strand being inserted binds to the strand being translated, forming double stranded mRNA.
3. This means ribosomes are unable to bind.
4. This prevents translation.

1. It requires DNA polymerase, primers, and DNA nucleotides.Note: I assume if you mentioned these throughout your answer you’d be fine.
2. Heat to 95 degrees C to break hydrogen bonds and separate strands.Note: you had to name the specific temperature and talk about hydrogen bonds being broken.
3. Reduce temperature (to 55 degrees C) so primers can bind/ anneal to the DNA strands.
4. Increase temperature (to 72 degrees C) so DNA (taq) polymerase can join the nucleotides to form the strands.

1. Complementary primers are needed for each RNA strand.
2. Base sequences differ between RNA strands.

1. Restriction endonucleases.
2. Cut DNA at specific base sequences/ recognition sites.Note: always mention the restriction endonucleases cutting DNA at specific base sequences.

1. They have different masses (due to having different numbers of amino acids).
2. They are charged.
3. They have different R groups.Note: I’m not really sure how the different R groups play a role, I’d just stick with the first two.

1. A short single strand of DNA.
2. With complementary bases to a gene.

1. Extract the cell’s DNA and add restriction endonucleases to create fragments of DNA after amplifying the DNA using PCR.
2. Separate the fragments using electrophoresis.
3. Treat the cell’s DNA to form single strands and expose its bases using a nylon membrane.
4. The radioactive probe will bind with the gene via complementary base pairing as its specific base sequence is complementary to it.
5. Use autoradiography to show the bound probe after washing away any unbound probes.

1. The polymerase chain reaction.
2. DNA fingerprinting.
3. Genome sequencingNote: mRNA and amino acid sequencing were rejected because viruses don’t produce mRNA (if they have DNA) or polypeptides.

Option 1:

1. Compare DNA base sequence.
2. Distinct groups will have different DNA.

1. Some people may be carriers of the disease.
2. It prevents suffering and death.
3. It allows for informed choices about having children.
4. The cost of screening may be cheaper than the cost of treatment

Note: additional one I’d add: It may allow the person to make lifestyle changes to prevent them getting the disease.

1. The provide the starting sequence for DNA polymerase.
2. They prevent the original DNA strands rejoining.