AQA A Level Biology复习笔记8.4.1 Recombinant DNA Technology

Recombinant DNA Technology

 

Recombinant DNA

  • The genetic code is universal, meaning that almost every organism uses the same four nitrogenous bases – A, T, C & G. There are a few exceptions
  • The genetic code is the basis for storing instructions that, alongside environmental influences, dictate the behaviour of cells and as a result, the behaviour of the whole organism
  • The universal nature of the genetic code means that the same codons code for the same amino acids in all living things (meaning that genetic information is transferable between species)
  • Thus scientists have been able to artificially change an organism's DNA by combining lengths of nucleotides from different sources (typically the nucleotides are from different species)
  • The altered DNA, with the introduced nucleotides, is called recombinant DNA (rDNA)
  • If an organism contains nucleotide sequences from a different species it is called a transgenic organism
  • Any organism that has introduced genetic material is a genetically modified organism (GMO)
  • The mechanisms of transcription and translation are also universal which means that the transferred DNA can be translated within cells of the genetically modified organism

 

Recombinant-DNA

 

Illustration of a maize plant that has recombinant DNA (DNA from Bacillus thuringiensis).

 

Recombinant DNA technology

  • This form of genetic engineering involves the transfer of fragments of DNA from one organism/species into another organism/species
  • The resulting genetically engineered organism will then contain recombinant DNA and will be a genetically modified organism (GMO)
  • In order for an organism to be genetically engineered the following steps must be taken:
    • Identification of the DNA fragment or gene
    • Isolation of the desired DNA fragment
    • Multiplication of the DNA fragment (using polymerase chain reaction - PCR)
    • Transfer into the organism using a vector (e.g. plasmids, viruses, liposomes)
    • Identification of the cells with the new DNA fragment (by using a marker), which is then cloned

     

  • Genetic engineers need the following to modify an organism:
    • Enzymes (restriction endonucleases, ligase and reverse transcriptase)
    • Vectors - used to deliver DNA fragments into a cell (eg. plasmids, viruses and liposomes)
    • Markers - genes that code for identifiable substances that can be tracked (eg. GFP - green fluorescent protein which fluoresces under UV light or GUS - β-glucuronidase enzyme which transforms colourless or non-fluorescent substrates into products that are coloured or fluorescent)

     

  • Genetic engineering is being used in the new field of science called synthetic biology
    • This is an area of research that studies the design and construction of different biological pathways, organisms and devices, as well as the redesigning of existing natural biological systems

     

 

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An overview of the steps taken to genetically engineer an organism (in this case bacteria are being genetically engineered to produce human insulin)

 

 

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