[docord]

hi there,

kaplan LN virology, has a fig.(II-5-8) followed by a table (t II-5-3) regarding this subject.

1. in the fig, we see +mRNA is considered the final product, i mean not an intermediate itself, the intermediates are shown in the grey area, whenever they are needed. so,we notice that -RNA ones don't need an intermediate actually, since an intermediate is by definition the product between the +mRNA and the virus genome itself; or at least, thats what both the fig n the text are trying to say.
2. but in the table, we encounter another definition. this time, the -RNA ones for example, do need an intermediate. that's because this time the final product is considered the progeny genome, not the mRNA, so the +mRNA would be and intermediate itself.
3. so, if a test ask you whether the -RNA ones need an intermediate or not, what would be the answer? i encountered the problem when i was dealing with test #18 (2008 edition, a 37 yo ambitious executive....) when it explains choice A .

 

[StepTaker]

Negative sense RNA viruses cannot be read by the host polymerases and therefore they have to be transcribed by the viral RNA-dependent RNA polymerase into a positive strand before it can be read.

So the intermediate here is the positive sense RNA strand, so yes they need an intermediate for that matter.

 

[docord]

Yes, that's actually what happens and the table also states that. I did a very bad mistake, the fig is talking about how they produce mRNA and it has nothing to do with the genome replication, which the table is talking about. :redcheeks;