A2 Biology (OCR) Processes 2

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  • Created by: MJ
  • Created on: 03-06-13 12:08
The basic process of genetic engineering
1) Required gene obtained 2) Copy of gene is packaged and stabilized in a vector 3) Vector carries gene to recipient cell 4) Recipient cell expresses gene through protein synthesis
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Insulin: mRNA finding
Specialised configuration methods separate mRNA from pancreatic tissue, reverse transcriptase synthesises a complementary DNA strand, making a copy of the template strand - single stranded.
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Copy of original gene is created by adding DNA polymerase and DNA nucleotides to the single strands, making a copy of the coding strand, the original gene in a molecule of cDNA. Unpaired nucleotides are added at each end to give comp. sticky ends
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Insulin: Plasmids
The sticky ends are complementary to the sticky ends of the plasmid, which are created by restriction endonuclease enzymes. The plasmids are mixed with the cDNA, only SOME take up the gene.
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Insulin: DNA Ligase
DNA ligase seals the plasmids which are now called recombinant as they contain genetically engineered DNA.
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Insulin: Bacteria
The plasmids are mixed with bacteria, only some take up the plasmids. The bacteria are grown on an agar plate, each cell produces a mound of identical cloned cells - a colony
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Insulin: Types of colony
Some bacteria didn't take up a plasmid, some took up a sealed up plasmid and some have taken up the recombinant plasmid and are transgenic
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Insulin: Genetic markers
Original plasmids have genes that make them resistant to ampillicin and tetracycline (antibiotic chemicals). The E.Coli bacteria is susceptible to both of them.
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Insulin: Restriction site
The restriction site of the restriction enzyme that cut the plasmid is in the place of the tetracycline resistance gene. So the recombinant plasmid allows ampicillin resistance but not tetracycline.
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Insulin: Replica plating
Some cells from the colonies are taken and placed on ampicillin agar, so only bacteria with a plasmid will grow.
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Some cells from the colonies are taken and placed on tetracyclin agar, so only bacteria with a non recombinant plasmid will grow. The cells that grew on the ampicillin agar, not the tetracyclin agar are the ones we want.
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Insulin: Production
We can grow the identified colonies and on a large scale, for example by a continuous batch culture in a industrial fermenter and harvest the insulin for human use.
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Primary Sucession
Pioneer community live on bare rock (the pioneer community), larger plants grow due to rock erosion and build up of dead/rotting organisms and replace/succeed the pioneers. Larger plants succeed each smaller plants until climax community reached.
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Succession on Sand Dunes
Pioneer plants (prickly sandwort, sea rocket) colonise sand above high water mark as they can tolerate salt water spray, a lack of fresh water and instable sand. Wind blown sand builds up around these plants.
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A mini sand dune forms and plants die/decay and nutrients accumulate. Bigger plants grow (sea sandwort, sea couch grass) colonise it. SCG 's underground stems stabilise sand.
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More stability, more nutrients lead to bigger plants growing (marram grass, sea spurge). Marram grass traps wind blown sand whilst its shoots grow taller, trapping more sand. More plants grow due to more nutrients and sand.
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Legumes grow (hare's foot clover, bird's foot trefoil) and the bacteria in root nodules convert nitrogen into nitrates. Larger plants (sand fescue, viper's bugloss) grow, stabilising the sand further.
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Apoptosis 1
Enzymes break down the cytoskeleton, cytoplasm becomes dense, organelles are tightly packed, cell surface membrane changes, blebs form, chromatin condenses and nuclear envelope breaks, DNA fragments.
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Cell breaks into vesicles and are taken up by phagocytosis (endocytosis of large solid molecules into a cell) so cellular debris is disposed of without damaging other cells and tissues. This process is quick.
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Artificial Vegetative Propagation: Cuttings
Section of stem cut at nodes. Cut end treated with plant hormones to encourage root growth (Auxins) and planted to create genetically identical plant.
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Artifical Vegetative Propagation: Grafting
A shoot section of a woody plant (rose bush/fruit tree) is grafted/joined to an already growing root and stem, a rootstock. The graft grows identical (genetically) to parent plant but not rootstock.
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Micropropagation: Callus tissue culture
Small piece of tissue taken from tip of shoot (explant) to be cloned and placed on a nutrient growth medium. Cells divide but do not differentiate. They form an undifferentiated mass of cells called a callus.
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After a few weeks, single callus cells are placed on a nutrient growth medium with hormones that encourage root growth. After a few weeks, they are transferred to a different nutrient growth medium with hormones that encourages shoot growth.
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The plants are then acclimatized in a greenhouse to grow further, then grown outside.
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Drosophilia development
Egg laid, mitotic divisions every 6-10 mins. A multinucleate syncytium is formed with no cell membrane. After the 8th division, the 256 nuclei migrate to the outer part. 11th - the nuclei form an outer layer around a yolk filled core.
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2 Segmentation
Division slows, the membrane invaginates the nuclei around the 6000 nuclei , forming a single outer layer. After 2/3 hours the embryo divides into segments corresponding to the organism's body plans.
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Md Mx Lb parts merge to form the head; T1-3 form the thorax; A1-8 form the abdomen. At the end of larval childhood, legs, wings and antennae form at metamorphosis.
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Card 2


Insulin: mRNA finding


Specialised configuration methods separate mRNA from pancreatic tissue, reverse transcriptase synthesises a complementary DNA strand, making a copy of the template strand - single stranded.

Card 3




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Card 4


Insulin: Plasmids


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Card 5


Insulin: DNA Ligase


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