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Biology revision – Recombinant DNA technology (Unit 21)
Producing DNA fragments
- Recombinant DNA tech allows genes to be manipulated, altered and transferred from
organism to organism
- These techniques have enabled us to understand how organisms work and to design
new processes and applications
- Number of human diseases result from individuals being unable to produce for
themselves various metabolic chemicals
- Many of these chemicals are proteins
- Treatment of such deficiencies previously involved extracting chemical from a human
or animal and introducing it into the patient
- This presents problems such as rejection by the immune system and infection risk
- Follows that there are advantages in producing large quantities of pure proteins from
other sources
o Techniques have been developed to isolate genes, clone them and transfer
them into microorganisms
- These microorganisms are then grown to provide a ‘factory’ for the continuous
production of a desired protein
- The DNA of two different organisms that has been combined in this way is called
recombinant DNA
- Resulting organisms is known as a transgenic or GM organism (GMO)
DNA of organism is accepted by different species and functions normally because:
- Genetic code is universal – can be used by all organisms
- Explains why the coded info on the transferred DNA can be interpreted
- Making of proteins is also universal in that mechanisms of transcription and translation
are essentially the same in all living organisms
o As a result, transferred DNA can be transcribed and translated within the cells
of the recipient organisms
o Proteins it codes for can be manufactured in the same way as they would be
within the donor organism
All indirect evidence of evolution
- Process of making a protein using DNA tech of gene transfer and cloning involves a
number of stages:
1. Isolation – DNA fragments that have the gene for the desired protein as isolated
2. Insertion – insert DNA fragment into a vector
3. Transformation – the transfer of DNA into suitable host cells
4. Identification – Identification of the host cells that have successfully taken up the
gene by use of gene markers
5. Growth/ cloning – of the population of host cells
- Before a gene can be transplanted it must be identified and isolated from the rest of
the DNA
- Given the required gene may consist of a sequence of a few hundred bases amongst
the million in human DNA, this is not easy
- Several methods of producing DNA fragments:
o Conversion of mRNA to cDNA using reverse transcriptase
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