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    writing notes to myself/internet just to make it stick - mainly all essay predictions


    Lac operon

    If non lactose is present - repressor binds to operator and inhibits transcription

    When lactose is present it binds to lac repressor changing its shape so it can longer bind to the operator site.
    RNA Polymerase can now begin the transcription of the structural genes - B Galactosidase and Lactose
    permease

    Succession
    Primary occurs on previously uninhabited land that has been newly expose eg bare rock from earthquake
    Secondary occurs on land cleared of all plants but still has soil present eg after forest fire

    Bare rock succession example -
    Pioneer species first species to colonise - adapted to harsh condition eg lichen
    Die and decay breaking down rock - humus produced - little layer of soil

    Little soil means water retained and nutrients - bigger plants can colonise that are better adapted to environment eg small flowering plants

    As more plants die and compose each seral stage has more soil - larger species can colonise with longer roots ect - they are better adapted than previous species. Each seral stage become more complex/diverse

    Climax community is reached where ecosystem is supporting largest and most complex of species (not forgetting animals) - equilibrium is reached (steady state)

    Oak tree is typical British climax species in woodland.
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    (Original post by Summerdays)
    Have you guys attempted the specimen?
    Yeah didn't find it too bad.. Managed to get a B which I'm happy with.. Made me revise more on the parts I got wrong

    what about you?
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    Protein synthesis - formation of a protein/polypeptide

    Transcription

    RNA polymerase binds to start of DNA to be copied - hydrogen bonds between bases break separating two strands
    One strand acts as a template to make mRNA copy

    RNA polymerase lines up free nucleotides alongside template stands - complementary base pairing (except U replaces T)

    Joined together making mRNA that is a complementary copy of the template strand and therefor the protein to be made

    Hydrogen bonds reform between DNA stands and it coils back into d helix

    RNA polymerase reaches stop codon and mRNA is stopped being made and detaches from DNA

    mRNA moves out of nucleus through nuclear pore and attaches to ribosome



    Translation - happens at ribosome in cytoplasm

    mRNA attaches to a ribosome - tRNA has amino acid binding site and an anticodon

    tRNA with anticodon complementary to the first codon attaches to first codon

    tRNA with anti condon complementary to second codon attaches to second codon

    the two amino acids carried by the tRNA molecules are bound by peptide bond

    the first tRNA molecules moves away leaving amino acid behind - 3rd tRNA binds to anticodon and peptide bond forms between 2nd and 3rd amino acid

    This process continues until stop codon is reached - a polypeptide chain is created and moves away from ribosome............
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    (Original post by mathsclown)
    Nice with the B, I would of been over the moon !
    Ehm good question and seriously not sure so to be on safe side, we should learn them not to tough


    p + q = 1
    p^2 + 2pq + q^2 = 1
    And the assumptions made when carrying it out are just: any mating is random, population is large, no genotype has a selective advantage and errr there is no mutation, migration or genetic drift
    My thoughts exactly And thanks, I had to redo my Chemistry this year (I got a C when I needed a B) so as I had the time I thought I'd have a go at this paper again.
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    I AM BACK... :P gonna do last 3 hour revision
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    3 Hour cram.

    Apoptosis: aka programmed cell death
    Occurs in soft tissue and skeleton
    May be triggered by a change in the body plan.
    Controlled by cytokines produced by immune system, hormones, growth factors etc
    This control can be inhibited by protein inhibitors.

    Enzymes break down cell cytoskeleton
    Cell Shrinks
    Chromatin Condenses
    Condensed chromatin is not transcribed

    Too much apoptosis leads to degeneration
    Too little apoptosis leads to tumours
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    Standard growth curve - normally followed by growth of microorganisms in closed culture


    Log phase - microorganisms adapting to new env. or producing enzymes etc..
    no energy for reproduciton used - growth slow

    Exponential phase - growth fast, doubles at regular interval - culture conditions most favourable

    Stationary phase - death rate same as reproduction rate
    mircobes die because not enough room/food sparse (intraspecific comp)

    decline (DEATH) phase - death rate exceeds reproduction rate - food very sparse and waste products are at toxic levels
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    (Original post by SwordStream)
    Standard growth curve - normally followed by growth of microorganisms in closed culture


    Log phase - microorganisms adapting to new env. or producing enzymes etc..
    no energy for reproduciton used - growth slow

    Exponential phase - growth fast, doubles at regular interval - culture conditions most favourable

    Stationary phase - death rate same as reproduction rate
    mircobes die because not enough room/food sparse (intraspecific comp)

    decline (DEATH) phase - death rate exceeds reproduction rate - food very sparse and waste products are at toxic levels
    aka sigmoid growth curve
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    Gene technologies - used to study genes and their functions

    Polymerase chain reaction (PCR)

    1) DNA sample mixed with free nucleotides, DNA polymerase and primers.

    2) Mixture heated to 95C to break hydrogen bonds

    3) Then cooled to about 50C so primers anneal to start of DNA fragment

    4) Heated again to about 72C and DNA polymerase lines up free floating nucleotides along each template by complementary base pairing, producing new DNA strands

    Cycle 1 produces 4 stands 2 produces 8 etc...
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    Cloning of plants

    Plants natural cloning
    Vegetative propogation... plants grow structures on their non-reproductive tissues e.g. leaves, stems roots, which grow into a new plant.
    An example: In the roots of elm trees, lie dormant sucker buds.
    These sucker buds are activated when there is any stress to the tree e.g. disease, damage
    These may be far away from the tree itself - to prevent the new trees from the original stress
    Suckers begin to form and eventually a new plant is created identical to the original.

    Plants artificial cloning
    Tissue culture. Stem cells (unspecialised cells)are taken from the roots of a plant,
    these are then sterilised to kill off any microrganisms as these would compete with the stem cells for nutrients.
    The stem cells are grown in a culture medium containing growth factors (e.g. auxins) and nutrients (e.g. glucose)
    The cells divide and grow into a small plant which is then placed in soil to grow into a full plant identical to original
    Micropropogation allows cloning of many plants quickly. Stem cells are taken from the developing clone and subcultured in other mediums

    Advantages: Can save plants from extinction, plants that take too long to germinate can be grown quickly, desireable genetic characteristics always passed on

    Disadvantages: Disadvantageous characteristics also passed on, expensive, reduced variation - one disease could kill whole crop
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    Animal cloning
    Reproductive - whole organism, used to clone animals to test drugs as it removes genetic variable making it more reliable
    Non-reproductive a.k.a theraputic - cells, tissues or organs created from embryonic stem cells, can replace damaged tissue without rejection issues

    Both use nuclear transfer: Egg cell taken from organism X and organism Y.
    X's egg cell becomes enucleated (Removing nucleus) and insert Y's nucleus
    Egg Cell stimulated to divide and grow genetically identical embryo to Y

    In reproductive: it is placed in a surrogate mother
    In non-reproductive: stem cells harvest from embryo

    Advantages: Desirable genetic characteristics, Infertile organisms can reproduce
    Disadvantages: Undesirable genetic characteristics, difficult, expensive, cloned org may not live as long
    Human cloning is illegal in the UK - ethical issues: lower quality of life, disturbance of family structure, destroyed embryos
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    Argh genomes & gene technologies now
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    (Original post by aimz08)
    Argh genomes & gene technologies now

    I have finished everything just doing behaviour.. god I hate it ;/
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    (Original post by ibysaiyan)

    I have finished everything just doing behaviour.. god I hate it ;/
    Did you do F214?
    I reckon I managed to get an A
    But this module I'm probably resitting in june!

    If I had a high B at AS, and two A's in the coursework and F214 what do you reckon I need to get in F215 to get an A or B overall?
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    (Original post by aimz08)
    Did you do F214?
    I reckon I managed to get an A
    But this module I'm probably resitting in june!

    If I had a high B at AS, and two A's in the coursework and F214 what do you reckon I need to get in F215 to get an A or B overall?
    I did it last year got 95% ish.. but I so want 90% on this f215 module.Ah That's good to hear Hmm I am guessing about 70 for a B ? in f215 :P
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    (Original post by ibysaiyan)
    I did it last year got 95% ish.. but I so want 90% on this f215 module.Ah That's good to hear Hmm I am guessing about 70 ? in f215 :P
    I honestly don't care what I get as long as I get into one of the uni's I've applied for.
    So glad I didnt get into medicine - Can't stand sciences anymore :P

    Any predictions? I'm just going through the list someone posted earlier...essay type questions. Can't do much else now.

    p.s. good luck for tomorrow ...doubt you need it as much as me though :P
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    Hey guys Ive just realised how pointless this exam is to me.

    If I get 0/150, Ill get a B in A Level Biology and if I get 130/150, Ill still get a B in A Level Biology.
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    (Original post by Chunkeymonkey62)
    Hey guys Ive just realised how pointless this exam is to me.

    If I get 0/150, Ill get a B in A Level Biology and if I get 130/150, Ill still get a B in A Level Biology.
    How do you work it out?
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    (Original post by Chunkeymonkey62)
    Hey guys Ive just realised how pointless this exam is to me.

    If I get 0/150, Ill get a B in A Level Biology and if I get 130/150, Ill still get a B in A Level Biology.
    Impossible.... lol
    60 ums is for a grade....
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    (Original post by ibysaiyan)
    Impossible.... lol
    60 ums is for a grade....
    wait wait...I need 70/150? that's it??
 
 
 
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