Shawaiz121
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Which disease is treated with drugs that have a similar molecular structure to DNA nucleotides?
A) cholera
B) HIV/AIDS
C) malaria
D) TB

The marking scheme says the answer is B but can anyone explain me how??/ Thanks
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macpatgh-Sheldon
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Hi,

Let us take his step by step.

To treat bacterial infections we use antibiotics e.g. penicillins which block the formation of bacterial cell wall so the *******s () burst and die or e.g. streptomycin that causes misreading of the genetic code in mRNA by binding to the ribosome so the blighters (bacteria!) make the wrong protein and again die.

OK you know HIV is a virus (Human Immunodeficiency Virus to be precise).

Do viruses have a cell wall?....................................... NO well done.

Do viruses have RER?................................................NO Ok you got it again.

So we cannot use above methods to tackle them - yes?

So what do we do to kill them?

OK they have RNA OR DNA don't they? Why don't we stop them making nucleic acids?


BRILLIANT - you got it in one! A drug like 5-fluorouracil will be incorporated into viral DNA instead of uracil - virus makes incorrect DNA!

Therefore ANSWER B is correct.

FOR A* candidates: HIV is a special type of virus called retrovirus [Greek retro = backwards] - it makes DNA out of RNA (other way round) - we can block the enzyme that does this [reverse transcriptase] with a drug like zidovudine.

Cholera is caused by Vibrio cholerae a bacterium so needs antibiotic.

TB is also caused by a bacterium (Mycobacterium tuberculosis), too.

Malaria is caused by a protozoan (Plasmodium species) - different way to treat.

DON'T worry about print in italics at A level if you are not a nerd!

M (specialist biology tutor/ex-medic)
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Shawaiz121
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(Original post by macpatelgh)
Hi,

Let us take his step by step.

To treat bacterial infections we use antibiotics e.g. penicillins which block the formation of bacterial cell wall so the *******s () burst and die or e.g. streptomycin that causes misreading of the genetic code in mRNA by binding to the ribosome so the blighters (bacteria!) make the wrong protein and again die.

OK you know HIV is a virus (Human Immunodeficiency Virus to be precise).

Do viruses have a cell wall?....................................... NO well done.

Do viruses have RER?................................................NO Ok you got it again.

So we cannot use above methods to tackle them - yes?

So what do we do to kill them?

OK they have RNA OR DNA don't they? Why don't we stop them making nucleic acids?


BRILLIANT - you got it in one! A drug like 5-fluorouracil will be incorporated into viral DNA instead of uracil - virus makes incorrect DNA!

Therefore ANSWER B is correct.

FOR A* candidates: HIV is a special type of virus called retrovirus [Greek retro = backwards] - it makes DNA out of RNA (other way round) - we can block the enzyme that does this [reverse transcriptase] with a drug like zidovudine.

Cholera is caused by Vibrio cholerae a bacterium so needs antibiotic.

TB is also caused by a bacterium (Mycobacterium tuberculosis), too.

Malaria is caused by a protozoan (Plasmodium species) - different way to treat.

DON'T worry about print in italics at A level if you are not a nerd!

M (specialist biology tutor/ex-medic)

Thanks sir!!!
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