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    i dont understand "the malaial parasite, plasmodium, is unable to exist in red blood cells with Hb^s (sickle shaped)."
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    I took this from my Scottish Higher notes so im not too sure if this is what you're looking for

    if you take the allele for normal blood (sickle cell not present) and S as sickle cell present.

    H is only partially dominant to S (incomplete dominance)

    Where S is homozygous (SS) this leads to death
    Where it is homozygous (HS) there is resistance to malaria but sickle cells is present. There is around 2/3 of normal blood cells and 1/3 of sickle cells (i think there is a resistance to malaria because the plasmodium is unable to exist in sickle cells...i think it may be because of the shape of plasmodium?)
    Where it is HH there is no resistance to malaria

    Hope this helps
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    (Original post by w8wizz)
    i dont understand "the malaial parasite, plasmodium, is unable to exist in red blood cells with Hb^s (sickle shaped)."
    Hb-S inside an erythrocyte means it only sickles when the partal pressure of oxygen decreases, which in normal circumstances might be at altitude etc. When a cell with Hb-S is infected by plasmodium, this causes the cell to sickle because of the low oxygen PO2 as plasmodium respires. This formation of a sickle shape makes it likely to be phagocytosed and destroyed, along with the plasmodium.
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    I don't suppose a friendly mod could merge this thread with http://www.thestudentroom.co.uk/t201073.html

    just to avoid confusion as the question has been answered in one thread
 
 
 
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