OCR Biology A2 (Unit 2) Processes 4

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  • Created by: MJ
  • Created on: 04-06-13 18:41
Lac Operon (Lactose Absent)
Regulator gene (I) expressed, repressor protein synthesised with allosteric binding site for lactose, one for operator region. RNA Polymerase cannot bind to Operator Region, structural genes untranscribed, proteins unsynthesised
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Lac Operon (Lactose Present)
Lactose binds to allosteric binding site of repressor protein, changing its shape, it dissociates from the operator region. RNA Polymerase binds to Promotor Region, Z+ Y expressed. Lactose taken up, hydrolysed and used for energy.
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Sequencing genomes
Chromsomes are mapped to find its location on genome, usually by locations of microsatelites, samples of genome are sheared into smaller sections of 100,000 BPS
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Sections are placed into bacterial artifical chromosomes (BACS) and transferred into E coli = cell libraries.
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Cells containing specific BACs are cultured and their DNA is extracted and cut by different restriction enzymes, giving varying sizes of fragments. The fragments are seperated by electrophoresis.
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Each fragment is sequenced using an automated process and computer programmes compare overlapping regions from different lengths of DNA caused by use of diff restriction enzymes.
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Electrophoresis
DNA samples are cut into fragments with restriction enzymes, samples are placed into wells at cathode end of gel, immersed in buffer solution, current passed through for 2hr
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DNA diffuses through gel to positive end as they are negatively charged, shorter lengths move faster as they aren't caught in the agarose gel, position shown with dye, nylon/nitrocellulose sheet placed over gel, pressed, DNA transfers (blotting)
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Golden Rice
Gene for Phyotene synthetase taken from daffodils and gene for Crt enzyme from Erwinia uredovora placed in rice genome. Phytoene synthetase converts precursor molecules into Phytoene, Crt1 converts phytoene into lycopone
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Lycopene is a precursor for carotenoids, it is converted by enzymes present in rice endosperm to caratenoid molecules and beta carotene
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Lac Operon (Lactose Present)

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Lactose binds to allosteric binding site of repressor protein, changing its shape, it dissociates from the operator region. RNA Polymerase binds to Promotor Region, Z+ Y expressed. Lactose taken up, hydrolysed and used for energy.

Card 3

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Sequencing genomes

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2

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Card 5

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3

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