Applications of biology

Unit 12

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  • Created by: Amy
  • Created on: 22-05-08 16:21

Recombinant DNA

DNA has the same structure of nucleotides in all organisms.

DNA that has been genetically engineered to contain DNA from another organism, is called Recombinant DNA.

Find gene DNA removed.

cut out the useful gene using restriction endonuclease enzymes which leave a sticky end

Prepare the other bit of DNA that you are joining the useful gene to which is called a vector.

The same restriction enzyme is used to cut out a section of the plasmid

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Recombinant DNA Continued

The sticky ends that are left have bases that are complementary to the bases on the sticky ends of the useful gene

Join the useful gene to the plasmid vector DNA - process called ligation

Hydrogen bonds form between the complementary bases of the sticky ends - tied together using ligase enzyme.

New DNA is called Recombinant DNA

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Reverse Transcriptase

Transcription is when mRNA is made from DNA. Reverse Transcriptase makes DNA from mRNA.

1) mRNA is extracted from donor cells

2) The mRNA is mixed with free DNA nucleotides and reverse transcriptase. The reverse transcriptase uses the mRNA as a template to synthesise a new strand of complementary DNA

3) The complementary DNA can be made double-stranded by mixing it with DNA nucleotides and polymerase enzymes. Then the useful gene from the double-stranded DNA is inserted intoa plasmid so the bacteria can make lots of the product of the gene.

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The Polymerase Chain Reaction (PCR)

1) The DNA sample is heated at 95 degrees C. This breaks the hydrogen bonds between the bases on each strand. But it doesn't break the bonds between the ribose of one nucleotide and the phosphate on the next - so the DNA molecule is broken into separate strands.

2) Primers are attached to both strands of the DNA - these will tell the enzyme where to start copying later in the process. They also the two DNA strands from joining together again.

3) The DNA and primer mixture are cooled to 40 degrees C so that the primers can fully bind on to the DNA

4) Free DNA nucleotides and the enzyme DNA polymerase are added to the reaction mixture. heated up to 70 degrees C. Free DNA nucleotides pair with their complementary bases. The DNA polymerase attaches the new nucleotides together into a strand, starting at the primers.

5) The cycle starts again. Each Cycle doubles the amount of DNA

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1) The DNA fragments are put into wells in a slab of gel. The gel is covered in a buffer solution that conducts electricity.

2) An electrical current is passed through the gel. DNA fragments are negatively charged, so they move towards the positive electrode. Small fragments move faster than large ones, so they travel furthest through the gel.

3) By the time the current is switched of, all the fragments of DNA are well separated.

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