Why is it that retroviruses are able to store genetic information as RNA before transcribing it to DNA?

Answer 1

Just a wild guess...

In the process of evolution of life from small molecules to complex systems it is believed that RNA molecules were the first macromolecules to act as catalysts and for storing information. Gradually these processes were taken over mainly by proteins and DNA respectively because these molecules can carry them out more efficiently. It would be reasonale to assume that during this transition elements which catalyzed synthesis of DNA from RNA templates appeared (maybe a form of the reverse transcriptase).

Retroviruses could be a remrant of those times adapted to the DNA-based world.

Answer 2

Hey, that's what I was going to say. As far as the mechanism they execute this (and why pretty much every other biological entity you've heard of can't) is that they contain a special enzyme called "reverse transcriptase. The virus, following cell entry, converts its RNA genome into a DNA copy with reverse transcriptase. The reason for this is that cells have an intrinsic immune response, where they recognize and chop up double stranded RNA sequences and then anything single-stranded that looks like it (known as RNAi). The DNA copy then gets inserted into the host genomic DNA by an enzyme called integrase. A significant amount of your own DNA is composed of old retroviral "fossil" DNA that don't really work anymore (twice as much as your own coding DNA). As for why RNA in the first place, though, I'd go with the fact that RNA is catalytic in addition to storing information and exactly what the other guys said.

Answer 3

No one knows answer to this question exactly; HIV virus does the same thing (before questioning i hope you you know about the reproduction of HIV if you dont contact me) for its reproduction many think its for this cause, but new studies proved that they replicate the DNA of the host and produce offsprings to destroy the lymph nodes by which the host cannot not give rise rise to anti-bodies.