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OCR 2010 A2 Biology Unit 2 - Control, Genome and Environment watch

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    (Original post by skatealexia)
    It depends.

    If the recessive allele is for white, for example bb, and this masks the expression of the allele for black say BB wherever it occurs, this is an example of recessive epistatis, as the white allele is masking the expression of the black allele. If the mouse is Agouti, it needs a mixture of both white and black hairs I guess, and it needs to be able to make the enzyme for both, so for example:
    Colourless->White->Agouti. If both alleles are needed for the agouti colouring and it does not say that one masks the expression of another, then this would be complementary epistasis as both of the alleles are needed to make agouti.


    Not sure if this makes sense.
    Yeah, it does, thanks!!!!
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    hey guys, Is there more than one way a bacterium can take up a plasmid?????
    the way i've learnt it is that you place the bacterium in ice cold calcium chloride- this makes the cell wall more permeable. you then add the plasmid and heat shock it...

    am i wrong in thinking this is the only way????
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    gah i'm seriously hating biology right now.

    and i just cant get started on chem, so thats again a pain...

    GAH!
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    (Original post by s_a_r_a)
    hey guys, Is there more than one way a bacterium can take up a plasmid?????
    the way i've learnt it is that you place the bacterium in ice cold calcium chloride- this makes the cell wall more permeable. you then add the plasmid and heat shock it...

    am i wrong in thinking this is the only way????
    You can use calcium salts and heat shock yeah. But there are more ways than that:

    Electroporation - pass a high voltage electric pulse through the cell which distorts the cell membrane
    Microinjection - inject the GE DNA straight into the cell using a micropipette
    Virus genomes - use viruses as a vector, they directly inject their DNA into cells they infect
    Ti Plasmids - found in agrobacterium tumefaciens, does the same as a virus, injects DNA into cells it infects
    Liposomes - wrap the plasmid with lipid molecules/in an artificial lipid molecule, fat soluble and so can cross the membrane.

    That covers the other ways.
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    (Original post by Falcon91)
    Me too, im so scared as well lol. Hopefully i just get at least a B. Its all i need for this

    And yeah, hate how its not like the spec as i usually get good marks in the spec! and a mock my college put together. Blast it!
    haha man i think you're pretty much set! :P
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    explain why genetic drift is seen better in small populations ????

    is it because the allele which helps the isolated population survive is more likely to be seen in the phenotype of gernation 1
    ???? help

    thanks
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    Hey guys I would appreciate some help here

    The cerebrum is divided into two hemispheres, the right and left. The outermost layer is the cerebral cortex. So what are the separate functions of the cerebrum and cerebral cortex? The book describes the structure of the cerebral cortex and then goes on to explain that "this region" is in control of emotions, thinking etc. But then it talks about the subdivisions of the cerebral cortex.

    So what does the cerebrum do exactly? I would appreciate if anyone could help me distinguish between the two because I really don't understand.

    My previous thought was:
    Cerebrum: Thought, intelligence, emotions, in control of voluntary muscle movement etc.
    Cerebral cortex: Sensory areas, association areas, motor areas

    I don't know if this is right.


    Should a question ask you to define the cerebral cortex and cerebrum separately, what should you reply? Or do we use these terms interchangeably?

    Thanks.
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    (Original post by Falcon91)
    You can use calcium salts and heat shock yeah. But there are more ways than that:

    Electroporation - pass a high voltage electric pulse through the cell which distorts the cell membrane
    Microinjection - inject the GE DNA straight into the cell using a micropipette
    Virus genomes - use viruses as a vector, they directly inject their DNA into cells they infect
    Ti Plasmids - found in agrobacterium tumefaciens, does the same as a virus, injects DNA into cells it infects
    Liposomes - wrap the plasmid with lipid molecules/in an artificial lipid molecule, fat soluble and so can cross the membrane.

    That covers the other ways.

    I've read that page on the OCR book, it leaves me kinda confused. does microinjection bypass the need for a vector? or is a plasmid injected into the cell?
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    (Original post by Falcon91)
    You can use calcium salts and heat shock yeah. But there are more ways than that:

    Electroporation - pass a high voltage electric pulse through the cell which distorts the cell membrane
    Microinjection - inject the GE DNA straight into the cell using a micropipette
    Virus genomes - use viruses as a vector, they directly inject their DNA into cells they infect
    Ti Plasmids - found in agrobacterium tumefaciens, does the same as a virus, injects DNA into cells it infects
    Liposomes - wrap the plasmid with lipid molecules/in an artificial lipid molecule, fat soluble and so can cross the membrane.

    That covers the other ways.
    thankssss.. will rep =)
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    (Original post by mikey_g)
    I've read that page on the OCR book, it leaves me kinda confused. does microinjection bypass the need for a vector? or is a plasmid injected into the cell?
    The microinjection needs a vector. What it is, the plasmid IS the vector which carries the gene. The micropipette can be used to inject the plasmid into the cell. The micropipette itself is not acting as a vector.
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    (Original post by The TSR Star.)
    Hey guys I would appreciate some help here

    The cerebrum is divided into two hemispheres, the right and left. The outermost layer is the cerebral cortex. So what are the separate functions of the cerebrum and cerebral cortex? The book describes the structure of the cerebral cortex and then goes on to explain that "this region" is in control of emotions, thinking etc. But then it talks about the subdivisions of the cerebral cortex.

    So what does the cerebrum do exactly? I would appreciate if anyone could help me distinguish between the two because I really don't understand.

    My previous thought was:
    Cerebrum: Thought, intelligence, emotions, in control of voluntary muscle movement etc.
    Cerebral cortex: Sensory areas, association areas, motor areas

    I don't know if this is right.


    Should a question ask you to define the cerebral cortex and cerebrum separately, what should you reply? Or do we use these terms interchangeably?

    Thanks.
    The cerebral cortex is a term that is used to desribe the thin layer of nerve cell bodies that are present on the outmost layer of the cerebrum. The cerebrum talks of the area as a whole. The cerbral cortex is just part of the cerebrum. The cerebrum (as a whole) is involved in what are termed 'higher' brain functions, such as emotional thought and response, features associated with intelligence such as resoning and judgment and the ability to override some reflexes. But there are many parts that make up the cerebrum, and these area collectively are known as the cerebral cortex- including sensory areas, motor areas and association areas, but also speech areas such as broca's area.
    I think that is the case, anyway. Hope it helped.
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    (Original post by Fabz2k9)
    explain why genetic drift is seen better in small populations ????

    is it because the allele which helps the isolated population survive is more likely to be seen in the phenotype of gernation 1
    ???? help

    thanks
    Genetic drift, firstly refers to changes in allele frequency that occur by random chance. Smaller populations will be more affected by this chance factor, compared to large populations where any changes tend to even out in the entire population.
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    (Original post by Falcon91)
    The microinjection needs a vector. What it is, the plasmid IS the vector which carries the gene. The micropipette can be used to inject the plasmid into the cell. The micropipette itself is not acting as a vector.
    Hi falcon! Hows it going?
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    (Original post by ViolinGirl)
    Hi falcon! Hows it going?
    Heyo, not bad...still worrying lol. I cannot stop now, my confidence is shot from january and i cannot stop complaining about it haha. But otherwise, not bad, how are you? how was your maths exam? :P
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    (Original post by Falcon91)
    Heyo, not bad...still worrying lol. I cannot stop now, my confidence is shot from january and i cannot stop complaining about it haha. But otherwise, not bad, how are you? how was your maths exam? :P
    I know, cannot stop. I got so much to do its not believable! Maths was ok, although that was the 'easy' exam. Worried about Core 4, cause I want an A* in that.

    Should we start our questioning round again?
    Describe interspecific competition and give an example.
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    bob
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    (Original post by Falcon91)
    Heyo, not bad...still worrying lol. I cannot stop now, my confidence is shot from january and i cannot stop complaining about it haha. But otherwise, not bad, how are you? how was your maths exam? :P
    I know, cannot stop. I got so much to do its not believable! Maths was ok, although that was the 'easy' exam. Worried about Core 4, cause I want an A* in that.

    Should we start our questioning round again?
    Describe interspecific competition and give an example.
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    (Original post by ViolinGirl)
    I know, cannot stop. I got so much to do its not believable! Maths was ok, although that was the 'easy' exam. Worried about Core 4, cause I want an A* in that.

    Should we start our questioning round again?
    Describe interspecific competition and give an example.
    Haha! Yeah sure.

    Interspecific competition - competition between two different species, this takes place when two species overlap in their ecological niche i.e. their roles in the ecosystem. The more the niche overlaps, the more intense the competition, they will compete for the same resources such as food and territory. They can affect each others population sizes, because both populations will be reduced to smaller sizes as less resorces will be available to both.

    However, they can affect each others distribution, if one area/habitat, one species population is better adapted to the env, its is more likely to obtain resources + outcompete the other species. this could lead to local extinction or just a small population size for the outcompeted species.

    However, in the competitive exclusion principle, other factors are eliminated. In the environment, theres likely to be many factors that have an impact, such as one species may have another source of food etc. This is seen in that bacterium experiment on that page of the OCR textbook (p aurelius and the other bacterium). A change in the conditions may favour one over the other as well.

    An example:
    Red and grey squirrels in the UK. Native red squirrels are outcompeted in some areas due to the foreign (American i believe) grey squirrel which has its population sizes increased because it is better adapted to its environment (i.e. there are less predators for it). Aaaand just for kicks:



    Explain how plants can be produced by tissue culture.
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    May someone please summarise the chain termination reaction for me? thanks!
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    (Original post by Falcon91)
    Explain how plants can be produced by tissue culture.
    Haha. Nice squirrel.

    I'll just expand on that a little as I was going over the bacterium thing yesterday. There are 2 species of parmecium, paramecium aurelia and parmecium caudamtum, and when these are grow together, and separately, the effect of interspecific competition can be seen. When separate the p.a is much better adapted at exploting the food resource present, so its growth rate is much faster compared to the p.c
    When grow together, the p.a, completely outcompetes the p.c, which dies off. This is an example of the competition exclusion principle. However in nature, there are many other factors involved that mean this will not be the only situation that occurs, the two species can coexist but one will be smaller than the other, and there are other environmental factors that can have greater effects on one or the other populations reducing/increasing their size.

    Now my question XD

    The technique by which plants are produced by tissue culture is called micropropagation by callus tissue culture. In this an small piece of tissue is taken from the plant to be cloned, this is called the explant, it is placed in a nutrient growth medium, which causes it to divide into a mass of undifferentiated cells called a callus. Individual callus cells can be removed and placed in first one medium/hormone that encourages root growth and then another that encourages shoot growth, they can then be placed in a greenhouse to acclimatise to conditions before they are planted outside.
    By this method, mass production of cloned plants is possible.

    What does the evidence from DRD4 receptors/dopamine show us?
 
 
 
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