Topic 19 Genetic Technology Test Flashcards
Describe how microarray analysis can be used to identify the genes switched on by the product of gene C
1.Obtain mRNA from cell expressing gene C
2. Reverse transcription of mRNA to produce cDNA
3. Add fluorescent labels to cDNA
4. Microarray has ssDNA probes
5. Each from a different gene
6. cDNA hybridises to ssDNA
7. Fluorescence shows the expressed genes
8. Intensity of fluorescence gives quantitative measure
Suggest how knowledge of the genes for these proteins could help in the treatment of asthma
- Sequence genes
- Predict amino acid sequences
- Model receptor protein 3d structure
- Find molecules that can block receptors
- Without triggering effects
- Limit the receptor protein production
Describe how the number of weed species resistant to herbicides has changed since 1960
- No resistance to any herbicide at start of use
- Resistant to photosystem II inhibitors - increases to 101-103 or from 1969 to 2013
- Resistant to ALS inhibitors - increase to 153 -155 or from 1981 to 2014
- Resistant to glyphosate - increase to 32/33 or from 1993-1995 to 2014
- ALS has steepest gradient/highest number of species
Explain how a weed species becomes resistant to herbicide
- Random mutation occurs
- Herbicide is selective pressure
- Mutant individuals survive
- and pass on mutant allele
- mutant allele increase in frequency
- to many generations
ALS is a globular protein consisting of four identical polypeptides each composed of 668 amino acids. (note: every amino acid is formed from three bases pairs)
State the number of base pairs in the gene that codes for an ALS polypeptide
668*3=2004 base pairs
Explain why resistance to ALS inhibitor herbicide can result from substitutions of amino acids that are far apart in the primary sequence
- After folding substituted amino acids are close together
- So there are different bonds
- Substituted amino acid causes change to protein, 3d structure
- Therefore, herbicide is unable to bind to active/allosteric site
Method 1: crossing a crop plant with a herbicide-resistant wild plant belonging to the same genus and then applying the herbicide
Method 2: causing mutations in the crop plants and then applying the herbicide
State two benefits of using method 1 and two benefits of using method 2 to develop herbicide resistance in crop plants
method 1:
1. Hybrid vigour/ reduces inbreeding depression
2. Increase in genetic variation
3. Increase in heterozygousity
4. It is cheaper
method 2:
1. No need to find a suitable (wild) plant / can proceed even if no resistant wild plant exists
2. Will not introduce unwanted alleles
3. No chance of disease transfer
Explain what the data in Table 3.1 suggests about the social and ethical implications of growing GM soybeans
- Decrease of GM soybeans decreases yield
- Increase of GM soybean increases yield
*Using GM crops(IMPORTANT-> CONTEXT):
ADVANTAGES - Increase food supply/decrease food cost
- Relieve hunger/starvation
- Less Herbicides are used
- Increase profits/improve economy
DISADVANTAGES - Unknown health consequences
- High cost of GM seeds
- Decrease in genetic varation
Suggest the main steps involved in creating recombinant DNA for this example of gene therapy
- Obtain therapeutic allele
- From mRNA of healthy person
- Use Electrophoresis for identification
- Use PCR to amplify gene
- Restriction endonuclease cut sections of DNA, leaving sticky ends to allow recombination.
- DNA ligase joining breaks in the phosphodiester backbone of DNA during repliation
- Add promoter
Explain why the fact that LCA is an autosomal recessive genetic disease makes it suitable for treatment with gene therapy
- Insert correct allele
- Need one allele per cell
- To cure disease
- To synthesise correct protein
- No need to edit faulty allele
Suggest why the retinal injection of gene therapy was used for LCA before it was trialled on other retinal diseases that gradually reduce the vision of people as they get older
- LCA patients are already blind
- Less likely to worsen for LCA patients
- Other eye age-related diseases may involve many alleles
Discuss the advantages of screening for genetic conditions
- Information about the increased risk of person having genetic conditions
- For instance breast cancer
- Allows people to prepare for late onset genetic conditions
- For example Huntington’s disease, Alzeimers disease
- Can identify whether fetus are going to develop a genetic condition
- So can give early treatment when born
- Allow parents to prepare for the birth of a child who will need treatment for a considerable time or even a lifetime
- Identifies carriers of genetic conditions
- Helps to provide early diagnosis
- Allow couples who are both carriers of a genetic condition to make decisions about starting a family
- Termination
Describe the principles of the polymerase chain reaction (PCR)
- Production of a larger number of copies of a length of DNA
- Rapid
- Only small samples of DNA needed
- DNA denatured into two strands
- Primer (DNA) added
- Annealing happens at 60-65 degrees celsius
- Complementary base pairing present
- DNA taq polymerase
- Replicates strand at 70-75 degrees celsius
- Heated again to separate strands
- Taq polymerase has high optimum temperature
- Does not need replacing each cycle
- Efficient process
Explain how RNA probes, used in this technique, select fragments of DNA
-RNA probe is single stranded
-There are complementary base pairs between RNA probes and DNA
-Different RNA probes base pair with different sticky ends of DNA
This technique is able to separated small DNA fragments that may different by only one nucleotide. Suggest why this technique is used to study genetic variation within species
-Genetic variation is due to mutation in base sequence
-Point mutation
-Small pore size of gel allows separation of various fragments
