19. Genetic Technology Qs Flashcards
Suggest why some methods of manufacturing genetically engineered insulin use eukaryotic yeast cells rather than prokaryotic bacterial cells. [2m]
- in yeast cells promoters already present
- have rough endoplasmic reticulum / Golgi body
- so insulin can be modified / insulin is in correct 3D conformation (due to folding)
Explain how gel electrophoresis separates DNA fragments cut with restriction endonucleases. [3m]
- phosphate groups are negatively charged
- so DNA fragments move to anode
- due to electric field when current applied
- larger fragments move more slowly / less far
4 advantages of using theoretical models in research, rather than testing possible drugs in the laboratory
3 reasons why theoretical modelling cannot completely replace laboratory trials in the search for new drugs
- faster / can try many diff. drugs in short period of time
- cheaper
- no need for laboratories
- initially no need for tests on animals/humans
- need to test that drug is effective / actually works
- to test for possible side-effects
- lab trials allow researchers to determine best drug dosage
Husband and wife already have a child with cystic fibrosis. Second child is tested (positive) for CF in very early pregnancy.
Explain the need to discuss the results of the test, a DNA banding pattern produced by electrophoresis, with a genetic counsellor. [4m]
- outcome of test needs explanation
- already have 1 affected child to care for / cost of care
- give advice on possibility of termination
- life expectancy is increasing with improved drugs
- but gene therapy is not as yet successful
- possibility of pre-implantation genetic diagnosis (PGD) on another occasion
State how genetic screening could reduce the number of cases of haemophilia. [2m]
- identify females who are carriers and have the recessive allele
- if embryo has ALLELE can choose abortion
- select unaffected IVF embryo to implant (after pre-implantation genetic diagnosis)
- women can choose not to have children
Explain why the production of memory cells (in primary immune response) prevents the gene therapy from working in long-term chronic conditions such as cystic fibrosis. [3m]
- repeat treatment causes more rapid immune response
- so target cells expressing new protein short-lived
- decrease in transgene expression on re-administration
Restriction endonuclease
- cuts DNA at specific site
- detail of cut; palindromic or blunt/sticky ends or staggered cut
- enzyme derived from bacteria
- destroys viral DNA in bacteria
Selective breeding programmes have been carried out in which Golden Rice was interbred with local rice varieties to produce varieties of Golden Rice that grow well in different localities.
Explain why the original Golden Rice had to be developed by genetic engineering, but locally-adapted varieties of Golden Rice could be developed by selective breeding. [3m]
- β-carotene genes come from a diff. species
- β-carotene genes not in rice, so cannot breed 2 diff. species together
- local varieties have desired characteristics
- crossing them with Golden Rice combines (best) features
Suggest how a variety of Bt cotton that is better adapted to dry conditions could be produced from the existing varieties of Bt cotton, WITHOUT using gene technology. [3m]
- selective breeding / artificial selection
- cross Bt cotton with a Bt variety that grows well in dry
- select offspring with Bt gene AND grow well in dry
- repeat crossing for several generations
Outline how genetic engineering gave T2A-1 rice the trait of insect resistance. [4m]
- gene from another species
- use restriction enzymes
- to cut plasmid/vector
- DNA ligase
- insert promoter
- RECOMBINANT plasmid
- introduced into rice cells
- gene expressed
- toxic protein produced
Outline the advantages of screening for the presence of mutations of the genes for breast cancer, BRCA1 and BRCA2. [6m]
If present,
- enable early treatment
- lifestyle changes
- preventative mastectomy
- regular check ups
- prevent unnecessary prolonged suffering if discovered and treated early
- prevent early death
If not present,
- removes worry
- help couples in family planning decision
Embryo biopsy
Removing a cell from an embryo (for testing)
Explain why Huntington’s disease cannot be treated with gene therapy. [4m]
- allele is dominant
- so will still be expressed even when normal, recessive allele is present
- gene therapy only used to treat recessive allele disorders
- cannot remove dominant allele
+ dominant allele affects tissues in many parts of the body
Genome
All the DNA in a person’s cells
*Do not write all the ‘genes’ b/c genome includes both coding and non-coding regions
