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    plz help sooooo hard

    1) (a) Why do the daughter chromosomes (previously chromatids) have a V shape at this stage?

    (b) What identifies the stage being anaphase of mitosis?

    2) Cancer treatement can involve chemotherapy. Cytarabine (cytosine arabinoside) is used to treat acute myeloid leukaemia (AML). Cytarabine is composed of the nitrogenous base, cytosine, linked to the 5 - carbon sugar, arabinoside triphosphate. This is structurally similar to the nucleotide, deoxycytidine triphosphate (dCTP), the form in which cytosine becomes incorporated into DNA during DNA replication, before the release of two of its phosphates (as pyrophosphate). When DNA nucleotides are added, the inner phosphate of the incoming nucleotide is attached to the carbon -3 of deoxyribose of the last nucleotide to be added.

    a) Suggest how cytarabine reduces the activity of a named enzyme that is involved in DNA replication

    b) Suggest how cytarabine (as cytosine arabinoside monophosphate) could inhibit further replication of DNA if one molecule of it became part of a growing DNA polynucleotide chain

    c) Suggest how cytarabine can be effective in the treatment of cancer, e.g. AML

    d) Suggest how cytarabine could cause an AML patient to become more prone to infection than before the treatment



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    (Original post by raman1)
    plz help sooooo hard

    1) (a) Why do the daughter chromosomes (previously chromatids) have a V shape at this stage?
    At what stage? Is there anymore details in the question?Mitosis or meiosis?

    (Original post by raman1)
    (b) What identifies the stage being anaphase of mitosis?
    You should go over the different phases and take a look at some pictures for examples. For anaphase, the spindle fibres pull the chromatids apart.

    (Original post by raman1)
    Cancer treatement can involve chemotherapy. Cytarabine (cytosine arabinoside) is used to treat acute myeloid leukaemia (AML). Cytarabine is composed of the nitrogenous base, cytosine, linked to the 5 - carbon sugar, arabinoside triphosphate. This is structurally similar to the nucleotide, deoxycytidine triphosphate (dCTP), the form in which cytosine becomes incorporated into DNA during DNA replication, before the release of two of its phosphates (as pyrophosphate). When DNA nucleotides are added, the inner phosphate of the incoming nucleotide is attached to the carbon -3 of deoxyribose of the last nucleotide to be added.

    a) Suggest how cytarabine reduces the activity of a named enzyme that is involved in DNA replication
    First of all, you can read from the text that cytarabine will stop mitosis occuring by inhibiting the cell replication part in interphase. The named enzyme you should you would be DNA Polymerase.
    (Original post by raman1)
    b) Suggest how cytarabine (as cytosine arabinoside monophosphate) could inhibit further replication of DNA if one molecule of it became part of a growing DNA polynucleotide chain
    I can't work this one out, my best guess would be that when it is attached to the DNA while it is replicating, the DNA starts producing more cytarabine, and then when this breaks off it becomes involved with other DNA replicating?


    (Original post by raman1)
    c) Suggest how cytarabine can be effective in the treatment of cancer, e.g. AML
    You should be able to work this one out, the very start of the text mentions chemotherapy, so it stops cell replication. Cancer is the build up of unhealthy/uncontrolled cell growth, which develops into a tumour.


    (Original post by raman1)
    d) Suggest how cytarabine could cause an AML patient to become more prone to infection than before the treatment
    Here you make a reference back to the text, it is used to treat myeloid leukaemia, which is the overdevelopment of immune cells. Stopping these replicating by using cytarabine can affect the body producing the healthy white blood cells, less white blood cells means your body will be more prone to infection.
 
 
 
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