7.4 gene technology

Cards (18)

  • what is recombinant DNA technology?
    • identify gene
    • make copies
    • transfer copies of DNA from one organism to another
  • why does recombinant DNA technology occur?
    • genetic code is universal
    • transcription and translation can occur in same mechanism
    • produce same amino acid sequence
    • in all organisms
  • how is reverse transcriptase used to produced DNA fragments?
    • mRNA thats complimentary to target gene used as template
    • mixed with free nucleotides that join via complimentary base pairing + reverse transcriptase
    • form phosphate sugar backbone
    • form cDNA (complimentary DNA)
  • How is recombinant DNA produced?
    • plasmid cut with restriction enzyme
    • target gene removed by cutting with same restriction enzyme
    • target gene spliced into open plasmid via DNA ligase (forms phosphodiester bond between plasmid + gene)
    • fragments joined via DNA ligase (covalently)
    • forms hybrid vector + other products
  • how do restriction enzymes work?
    • active site complimentary to DNA recognition sequence
    • hydrolyses DNA to leave blunt and sticky ends
    • target genes are cut with same restriction enzyme so complimentary base pairing can occur
  • sticky ends = unpaired bases at the end
    blunt ends = no unpaired bases at the end
  • how is recombinant DNA inserted into other cells?
    • virus vectors
    • gene guns
  • how do you identify recombinant cells?
    • use plasmid vector with antibiotic resistant gene
    • vector contains 2 marker genes:
    • marker gene 1 = identify if cell has taken up plasmid or not. cells with plasmid gain antibiotic resistance
    • grown on medium, non recombinant cells will die
    • marker gene 2 = identify if cell has taken up hybrid vector.
    • foreign DNA in marker gene 2. cells with hybrid gene cant make this DNA
    • cell with hybrid vector not resistant. so will die
    • ampicillin test on replica plate
    • colonies that grow on first plate but not on replica (ampicillin) plate are recombinant.
  • how are viruses used as vectors?
    • in latency
    • nucleic acid inserted into DNA of host cell
  • how are gene guns used as vectors?
    • air pressure used
    • fires heavy metal particles
    • with the target gene on into cells.
  • what do you do to allow bacteria to take up recombinant dna?
    • soak in ice cold calcium chloride
    • heat shock of 42 degrees for 2 mins
  • what are knockout mice? what are they used for?

    • mice with one gene silenced
    • similar gene is inserted so the original is impossible to read
    • used to understand gene function
    • to test for treatments
  • how are knockout mice formed?
    using embryonic stem cells...
    • DNA sequence changed to inactivate gene
    • mutant gene injected in embryo
    • resulting offspring will have cells with mutant gene or normal genes
    • sperm cell with mutant genes are isolated
    • male mice bred with normal female. producing heterozygous children
    • heterozygotes bred together to produce homozygous recessive mice with mutant gene.
  • how can plants be genetically modified?
    using agrobacterium tumefaciens...
    • Ti plasmid removed from bacterium
    • T-DNA cut with restriction enzyme
    • foreign DNA cut with the same restriction enzyme
    • foreign DNA inserted into T-DNA of plasmid
    • plasmid reinserted into bacterium. and inserted into chromosome of plant cell
    • plant cell grown on culture
    • plant generated from clone and all cells contain foreign gene
  • GM soya plants
    • resistant to herbicides
    • resistant to fungus pathogen
    • resistant to droughts
    • produces less linoleic acid
    • produces more oleic acid
  • how does linoleic and oleic acid affect GM soya plants?
    linoleic acid
    • polyunsaturated
    • oxidises soya bean - doesnt last as long
    oleic acid
    • monounsaturated - healthier
    • not easily oxidised - lasts longer
  • benefits of recombinant gene technology?
    • medicines can be produced without animal harm
    • improved agriculture - less pesticides used
    • GM crops can grow on previous unsuitable soil
    • improved nutritional quality
  • risks of recombinant gene technology?
    • modified organism - unforeseen genetic effects and disease
    • ecosystems - unforeseen effect on food web
    • biodiversity - reduces genetic diversity due to selective breeding
    • human society - could be taking away other country income
    • farmers - wont be able to afford benefits of GM crops