GENE TECHNOLOGIES

• In stage 1, an enzyme is used to cut open the plasmid.

  Name the type of enzyme used to cut open the plasmid?

  Restriction endonuclease
•   In stage 1, another enzyme is used to insert the desired gene into the plasmid DNA.

  Name the type of enzyme used to insert the gene into the plasmid?

  DNA ligase
•  In stage 4, some plant cells had plasmid DNA only in their cytoplasm. In other plant cells, the plasmid DNA had become inserted into plant DNA in the nucleus.

  In stage 5, only cells with plasmid DNA inserted into the plant DNA in the nucleus grew into plants where all the cells contained the desired gene.

  Explain why some of the plants in stage 5 contained the desired gene in all of their cells and others did not.?

  For plants that contained desired gene:

  DNA was copied with host DNA/ inside nucleus

  Passed on by mitosis

  Produces genetically identical cells
• The desired gene in the diagram was from an insect. In stage 6, the plant containing this gene was able to use it to synthesise an insect protein.

  The plant is able to synthesise the insect protein. Explain why this is possible.?

  Genetic code us universal in DNA - always codes for same amino acids

  Insect DNA can be transcribed

  Can be translated the same in all organisms
• A gene was broken into fragments using enzyme Z. The mixture of fragments produced was then separated by electrophoresis.

  (a)     What type of enzyme is enzyme Z??

  Restriction Endonuclease enzyme
• Explain why base pairs are a suitable way of measuring the length of a piece of DNA?

  DNA made of base pairs

  Each base pair is same length along backbone
•  Enzyme Z recognises a particular sequence of bases in the gene. How many times does this sequence appear in the DNA of this gene??

  5
• The DR region consists of non-coding base sequences.

  What is meant by a non-coding base sequence??

  Does not code for amino acid/ tRNA/ rRNA
• Name the process by which the base sequence of a spacer is lost from a DR region?

  Deletion mutation
• The scientists cloned the DR region DNA in vitro before testing for the presence of spacers.

  Give the name of the method they used to clone the DNA in vitro.?

  The polymerase chain reaction
•  Explain how the use of DNA probes produced the results in the diagram.?

  Probes are single stranded/ have a specific base sequence

  Complementary base sequence on specific space
• Doctors can use the method with DNA probes to identify the specific strain of M. tuberculosis infecting a patient. This is very important when there is an outbreak of a number of cases of tuberculosis in a city.

  Suggest and explain why it is important to be able to identify the specific strain of M. tuberculosis infecting a patient.?

  To see if strain is resistant to any antibiotics

  So can prescribe effective antibiotic

  ORRR:

  To see whether any vaccine works against strain to see which vaccine to produce

  so can stop spread
•  Explain why the scientists used the same restriction endonuclease enzymes on each DNA sample.?

  Cut DNA at same base sequence

  SO can get required gene
• Explain why primer A3 and primer A4 only bind to specific DNA fragments.?

  Each has specific base sequence

  That is complementary to R
•   Use all the information given to explain the results in Figure 1.?

  Fragments L from parents rr - as all longer fragments

  Fragments N from parent RR, as all shorter fragments

  M from offspring heterozygous , Rr as has both
• The scientists wanted to know on which chromosome the gene with alleles R and r was located. From the flies with genotype RR, they obtained cells that were in mitosis and added a labelled DNA probe specific for allele R. They then looked at the cells under an optical microscope.

  Explain why they used cells that were in mitosis.?

  Cells in mitosis - chromosomes visible

  So can see which chromosome DNA probe attached to
• Explain why the scientists carried out the control experiment with the non-resistant flies. ?

  For comparison with resistant flies

  TO see death rate in non resistant
•  The scientists concluded that the resistance of the flies to the insecticide is partly due to increased activity of PM but other factors are also involved.

  Explain how these data support this conclusion. (4)?

  PM involved:

  fewer resistant flies die

  more inhibited flies die rather than resistant

  inhibited flies die faster

  OTHER FACTORS:

  Some resistant flies die

  but with inhibitor still have greater resistance
•  The geneticist told the couple they were both carriers of the mutated gene.Explain how he reached this conclusion.?

  Carriers are heterozygous - so have one normal and one mutated gene

  Both have DNA that binds about 50%

  Probe binds to dominant allele so only one copy of exon in their DNA
• The DNA probe the geneticist used was for an exon in the DNA, not an intron. Explain why.?

  Introns not translated - in mRNA

  Mutations of these exons affect amino acid sequences that produce faulty protein

  So important to know if parents have exons affected - rather than introns
• To make the DNA probe, the geneticist had to find the base sequence of the normal gene. Once he had copies of the gene, what methods would he use to find the base sequence of the gene??

  Restriction mapping

  DNA / base sequencing of fragments
• Describe the effect on growth of transferring the gene for GB into this plant.?

  No effect at 25°C

  keeps growing at 30°C and 35°C

  above 35°C falls but grows more than plant without GB
• The scientists concluded that the production of GB protects photosynthesis from damage by high temperatures.

  Use these data to support this conclusion.?

  Significant different - SEs do not overlap
• Use the data from Figure 2 for plants that do not produce GB to explain the effect of temperature on changes in dry mass of the plants shown in Figure 1.?

  AS temp increases:

  enzyme activity decrease

  less photosynthesis so fewer sugars formed

  less respiration - so less ATP for growth

  Less energy for mitosis
•  Rubisco activase stops working when it attaches to a thylakoid.

  Use your knowledge of protein structure to explain why.?

  Rubisco attaches to thylakoid and changes tertiary structure - so active site changes

  prevents ES complexes forming
• Use information from Figure 2 and Figure 3 to suggest how GB protects the crop plant from high temperatures.?

  GB prevents binding of rubisco to thylakoid membrane

  Prevents it up to 35°C;

  so rubisco remains active

  so photosynthesis (LIR) still happens
•   The scientists’ hypothesis at the start of the investigation was that crop plants genetically engineered to produce GB would become more resistant to high environmental temperatures.The scientists developed this hypothesis on the basis of previous research on crops that are grown in hot climates.

  Suggest how the scientists arrived at their hypothesis.?

  Looked for information / journals, on crop plants that grow at high temperatures

   (Crop plants cited in this research) contain / make GB

  So assumed making plants produce GB makes them resistant to high temps
• People can be tested to see whether they have an allele for this gene with more than 36 CAG repeats. Some doctors suggest that the results can be used to predict the age at which someone will develop Huntington’s disease.

  Use information in the graph to evaluate this suggestion.?

  Negative correlation

  Wide range

  Overlap

  Other factors may be involved
•  Huntington’s disease is always fatal. Despite this, the allele is passed on in human populations. Use information in the graph to suggest why.?

  Age of onset can be high - symptoms appear later in life

  So individuals already have children and allele passed on
•  The diagram only shows part of the gel. Suggest how the scientists found the number of CAG repeats in the bands shown on the gel.?

  Run fragments of known length - CAG repeat at same time
•  Two bands are usually seen for each person tested. Suggest why only one band was seen for Person L.?

  Homozygous - CAG fragments are all the same length
• Suggest why the plasmids were injected into the eggs of silkworms, rather than into the silkworms.?

  If injected into egg - gene gets into all/most cells of silkworm

  so gets into cells that make silk
•  Suggest why the scientists used a marker gene and why they used the EGFP gene.?

  Not all eggs will successfully take up plasmid

  silkworms that have taken up gene will glow
• The scientists ensured the spider gene was expressed only in cells within the silk glands.

  (c)     What would the scientists have inserted into the plasmid along with the spider gene to ensure that the spider gene was only expressed in the silk glands of the silkworms??

  Promoter region
•  Suggest two reasons why it was important that the spider gene was expressed only in the silk glands of the silkworms.?

  So protein can be harvested

  Fibres in other cells might cause harm
•  Describe how genetic fingerprinting may be carried out on a sample of panda DNA (6)?

  DNA is cut

  Using restriction enzymes

  Use electrophoresis

  Separates according to length/ mass

  Transfer to nylon membrane

  Make single stranded

  Apply probe

  Radioactive/ fluorescent
• Explain how genetic fingerprinting allows scientists to identify the father of a particular panda cub?

  All bands in cub which done come from mother

  Must be in father DNA fingerprint
• When pandas are bred in zoos, it is important to ensure only unrelated pandas breed. Suggest how genetic fingerprints might be used to do this?

  Select pairs with dissimilar DNA fingerprints
• Suggest why panda DNA is found in faeces?

  Cells from panda in faeces/ gut cells / blood cells
•  Explain why the PCR is carried out on the DNA from the faeces.?

  TO increase amount of DNA