AAMC Section Bank B/B #19

[AWolfman]

A vDNA sequence encoding a protein is inserted into a host genome by IN. The protein is translated from the hypothetical mRNA sequence shown.

5

–GGCAACUGACUA–3

Based on the passage, the segment of the original viral genome that encoded this protein had what nucleotide sequence?

Answer: The sequence of the nucleotide in the original viral genome will be the same as that of the transcribed mRNA.

Why is the mRNA strand not complementary to the vDNA?

---

Members don't see this ad.

 

[aldol16]

Why is the mRNA strand not complementary to the vDNA?

mRNA is complementary to antisense DNA, not sense DNA.

 

[AWolfman]

ahhh thanks

 

[@Hazel-rah]

Could you explain this a little more @aldol16 ?
The vDNA is from HIV, a retrovirus. But anyways, I don't understand this question.

If that is the mRNA, wouldn't you work backwards to find the complementary DNA strand from which the mRNA was transcribed?

 

[aharr157]

The viral genome is RNA itself for a Retrovirus


Sent from my iPhone using SDN mobile

 

[aldol16]

The vDNA is from HIV, a retrovirus. But anyways, I don't understand this question.

The vDNA is going to be two-stranded since it's DNA and not RNA. Therefore, there will be a sense strand and an anti-sense strand. Sense strands are not transcribed because they don't code for proteins. It's the antisense strand that codes for a protein and thus will be transcribed. Therefore, the mRNA will be complementary to the antisense strand, which is complementary to the sense, or coding, strand. Complementary to a complement is just an identity and thus the mRNA sequence will be identical to the sequence present on the sense, or coding, strand.

 

[aldol16]

If that is the mRNA, wouldn't you work backwards to find the complementary DNA strand from which the mRNA was transcribed?

To add more, this "complementary DNA strand" you refer to is the anti-sense strand, which is not a coding strand.

 

[Squish miss]

i still don't get it
what is HIV. is it DNA to begin with

okay this is my thought process

the original has to be an RNA cause it says DNA was made from RNa.

it says protein is translated from (I'm only giving the last five AA)
5'-GACUA-3' the question

so the DNA strand must have been
3'CTGAT-5'

BUT HIV is an RNA (you have to go back to the what the VIRUS is actually. an RNA
so thats complement to

the 3'CTGAT-5', which is 5'GACTA-3'. THE THING THAT IS BEING TRANSLATED.


RIGHT. I THINK IT JUST HELPS TO DRAW IT OUT FOR THOSE OF US WHO ARE STRUGGLING

 

[aldol16]

what is HIV. is it DNA to begin with

HIV is an RNA virus. It injects RNA into the host cell. With that package also comes reverse transcriptase, integrase, and protease. These enzymes tell you how HIV works. First, reverse transcriptase makes DNA from that injected RNA. This DNA will, of course, be complementary to the injected RNA. Integrase then integrates the viral DNA into the host genome. Then protein synthesis occurs by the cell's usual mechanisms, namely that DNA is transcribed into mRNA, which will be complementary to the integrated viral DNA and therefore identical to the initial injected viral RNA, which is translated into protein. HIV protease then clips that protein at specific spots to activate it.