Reverse Transcriptase

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Dr. To Be

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Good morning.

I am going over the different viruses and i am currently over thinking a simple fact (I think!). Why is reverse transcriptase is required to be carried by viruses? Is because viral RNA is translated by host ribosomes so it waits until that is done and the host cell provides the reverse transcriptase? Or am I wrong? Please Advise.... Thank you!!!

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You are correct in that the viruses need the host ribosomes and other machinery to replicate and create new virions. Eukaryotic and bacterial reverse transcriptases are both RNA-dependent DNA polymerases which produce complementary DNA. Not all viruses require reverse transcriptase. For retroviruses (RNA-based) the enzyme is needed for the transcription of viral RNA to produce a double stranded DNA that can be inserted into its host genome. Once incorporated, the virus can replicate using the host machinery.

In eukaryotes, the enzyme replicates the entire genome or the transposable genetic units including the gene for the enzyme itself. This is done so that the enzyme can fulfill its role of synthesizing identical complementary DNA of the original units, so the virus is able to produce infectious viruses or transposable units when incorporated back into the host DNA.

Another reason to be be aware of this enzyme for the MCAT is that its a popular site for drug mechanisms, which means the MCAT can be more creative with what they ask.
 
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Thank you so much! I miswrote the question. Why is it required to be carried by the host cell is what I meant to say.
 
Correct me if I'm wrong. The virus itself carry the reverse transcriptase not the host cell. It doesn't make sense if the host cell is the one that carry it. Host cell don't need to reverse transcribe while the virus do since virus contain RNA that need to be made into DNA.
 
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Correct me if I'm wrong. The virus itself carry the reverse transcriptase not the host cell. It doesn't make sense if the host cell is the one that carry it. Host cell don't need to reverse transcribe while the virus do since virus contain RNA that need to be made into DNA.

You are mostly correct. Eukaryotics cells and non-retro viruses can also contain and utilize RT. Euk cells can use their RT for genetic transposition (DNA-->RNA, move to another section of the genome, RNA-->DNA).

For the purposes of the MCAT, I would bet that these rare uses of RT are unlikely to be tested, unless they mention it in a passage specifically. Focus on viral usage of RT. Good luck!
 
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