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    could someone explain polygenic/monohybrid inheritance/ locus things/ continuous variation pleeeaaase ?

    all a blur to me :?
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    (Original post by jooh_23)
    could someone explain polygenic/monohybrid inheritance/ locus things/ continuous variation pleeeaaase ?

    all a blur to me :?
    polygenic inheritance- some characteristics show continuous variation such as height, this is because they are controlled by genes at many loci.
    locus/loci- is the possition of a gene on a chromosome.
    such characterisitics are also effected by environmental factors.
    And some characteristics show discontinouos variation, they are controlled by genes at a single loci and the environment has little or know effect on it. such as blood group.
    hope i helped, i dont like this topic much.
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    Hi, I just wanted to ask do we need to know any specific examples of endemic species?? Thanks


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    (Original post by Rubyturner94)
    polygenic inheritance- some characteristics show continuous variation such as height, this is because they are controlled by genes at many loci.
    locus/loci- is the possition of a gene on a chromosome.
    such characterisitics are also effected by environmental factors.
    And some characteristics show discontinouos variation, they are controlled by genes at a single loci and the environment has little or know effect on it. such as blood group.
    hope i helped, i dont like this topic much.
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    thank you!!! x in the snab book its in a huge block of text, makes no sense at all
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    can someone give me all the points on zoos please? like a model answer?

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    (Original post by StephenNaulls)
    - A polypeptide chain is synthesised in a ribosome when peptide bonds are formed between many amino acid monomers; the ribosome is attached to the cisternae of the rER.
    - The polypeptide chain moves into the cisternal space of the rER, where it undergoes further processing in order to achiever a tertiary structure.
    -The rER packages the protein into a vesicle.
    - The vesicle fuses with the cis-face of the Golgi apparatus, thus causing the protein to enter the cisternal space.
    - In the cisernal space, carbohydrate chains are added/trimmed in order to create a glycoprotein, for example, which creates a quaternary structure (not all proteins do this).
    - The Golgi apparatus packages the glycoprotein into a vesicle at the trans-face.
    - The vesicle fuses with the phospholipid bilayer; secreting the protein via exocytosis.

    So they are involved in the processing and packaging of proteins- complex proteins could not be created without them.

    Hope that helped
    thank you
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    (Original post by The Assassin)
    , my notes are awesome.
    I know they are! (you didn't write that in the quote )
    I spotted something in the notes...
    In the table of starch and cellulose it said starch had h bonds with h20 hence soluble... (you've probably corrected since then but I downloaded the first version)
    Anyway, how's revision going?
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    gguys what is a totipotent and pluri potent cell.please provide the most info u can give.
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    (Original post by fadyfox95)
    gguys what is a totipotent and pluri potent cell.please provide the most info u can give.
    Totipotent - can basically give rise to all cell types

    Pluripotent - Can give rise to most except embryonic cells.
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    Can someone he;p with this please?

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Size:  135.3 KB - why is it that though? I thought it was 5. is it a specific thing we need to know? then why does it say using the graph?
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    (Original post by yarshad)
    Totipotent - can basically give rise to all cell types

    Pluripotent - Can give rise to most except embryonic cells.
    thanks, but I know that what I wanted to know which one has switched off and on genes, this stuff dude.
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    (Original post by yarshad)
    Can someone he;p with this please?

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Size:  135.3 KB - why is it that though? I thought it was 5. is it a specific thing we need to know? then why does it say using the graph?
    It's just graph skills and knowledge of interphase. Basically, it's the point from when the DNA begins to increase to where it finishes increasing which is about 3.75.
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    (Original post by yarshad)
    Can someone he;p with this please?

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Size:  135.3 KB - why is it that though? I thought it was 5. is it a specific thing we need to know? then why does it say using the graph?
    the S phase is when the DNA content has DOUBLED, the x axis states the amount of DNA. at 7.5 it is constant, from 7.5 to 10 it is rising and at 10 it has doubled. therefore the time taken is 3.5.
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    (Original post by fadyfox95)
    thanks, but I know that what I wanted to know which one has switched off and on genes, this stuff dude.
    they both have genes switched on, but totipotent has all genes switched on, and pluripotet has some but not all.
    correct me if i am wrong.
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    (Original post by fadyfox95)
    thanks, but I know that what I wanted to know which one has switched off and on genes, this stuff dude.
    If a totipotent stem cell can become any kind of cell, surely you can safely assume for yourself that it has no genes switched off?

    Conversely, pluripotent stem cells has some inactive genes. The presence of a chemical may cause some to become active/inactive also; this means that a different mRNA strand is transcribed, as the base sequence that determines the mRNA strand has changed. As a result, a different protein is synthesised. Since proteins determine the structure of the cell and control it's actions, the cell begins to change in order to carry out a specific function. The presence of the proteins causes more proteins to be made which furthers this effect; the cell has differentiated, or became specialised and this process is difficult to reverse.

    Was that the sort of thing you were looking for?
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    (Original post by fadyfox95)
    gguys what is a totipotent and pluri potent cell.please provide the most info u can give.
    1)Stem cells are unspecialised cells that can differentiate into any cell type.
    In stem cells (totipotent) they have all the same genes but not all are expressed because not all are on/ active, hence ability to differentiate.
    2)Under the correct conditions certain genes are activated others are inactivated (implying all are on in totipotent, my bad) and thus the whole protein synthesis process happens.
    3) MRNA is transcribed from the active gene at DNA, then transported out nuclear membrane to ribosome for translation of protein.(from active gene)
    4)The protein made determines cel structure and cell processes, including, which genes are switched on or off. And it's these changes that cause the cell to specialise and differentiate.

    A totipotent stem cell has the ability to differentiate into any cell type including extra embryonic cells e.g placenta and umbillical cord cells, whilst pluripotent can differentiate into any cell but the extra embryonic. Adult bone marrow stem cells are limited in their
    differentiation capabilities, whilst early foetus stem cells are totipotent...
    There's ethical issues surrounding the use of embryo stem cells, the embryo was viable, and also the idea it's a genetically unique individual thus has a right to life from fertilisation( depends on where life starts to some)

    Ermm, then theres some that feel that unfertilised embryos can be used as they're not viable (can't make a fetus) and only survive a few days, but they can't develop into all sorts
    of specialised cells.

    Erm, use the assassins notes, they're pretty good and the CGP revision guide for more!
    Hope that helps! Sorry if any mistakes or typos *tell me where if I have, gotta fix it *

    Right finally dig it,
    Toti - all on
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    (Original post by billyfisher100)
    It's just graph skills and knowledge of interphase. Basically, it's the point from when the DNA begins to increase to where it finishes increasing which is about 3.75.
    So confused. DNA begins to increase? that's after 5 hours isn't it? :L it finishes increasing at 10 hours

    (Original post by Rubyturner94)
    the S phase is when the DNA content has DOUBLED, the x axis states the amount of DNA. at 7.5 it is constant, from 7.5 to 10 it is rising and at 10 it has doubled. therefore the time taken is 3.5.
    ?????? the X axis states the time in hours? :L

    What???
    7.5??
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    (Original post by fadyfox95)
    thanks, but I know that what I wanted to know which one has switched off and on genes, this stuff dude.

    Totipotent, all genes switched on...

    Pluripotent - less are switched on..

    I'm guessing lol
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    (Original post by anonymouspie227)
    Stem cells become specialised because different genes are switched on.
    If this is the case, then wouldnt all the genes be off in totipotent as it can specialise into any cell type? Whilst pluripotent a few?

    Edit: I think I'm wrong lol, ignore me.
    Scroll up to my explanation. It's because genes are transcribed to create proteins, which alter the shape, and, as a result, function of the cell. If no genes were turned on no proteins would be made- therefore the cell couldn't differentiate as proteins are what causes this to occur!

    Do you get why now?
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    (Original post by StephenNaulls)
    Scroll up to my explanation. It's because genes are transcribed to create proteins, which alter the shape, and, as a result, function of the cell. If no genes were turned on no proteins would be made- therefore the cell couldn't differentiate as proteins are what causes this to occur!

    Do you get why now?
    Yea I dig it now
    Moment of madness!!!

    So as pluripotent cells can't differentiate into certain cell types those genes are switched off!
    Thanks!
 
 
 
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