Why/How could RNA have existed before DNA?

Question

Why/How could RNA have existed before DNA?

Answer 1

Because Plants Were Around Before Animals

Answer 2

RNA can catalyze its own duplication

Answer 3

An important characteristic of life is the ability to reproduce. In 1993, scientists found small molecule of synthetic RNA that could quickly make copies of itself. This provided part of the evidence used to explain how RNA molecules led to the evolution of the more complicated DNA molecule (which contains the genetic code for protein synthesis such as enzymes), which in turn led to protocells and then living cells.

Answer 4

it is believed that in an RNA world, RNA was both informational macromolecule (like DNA) and enzyme (like proteins)

there is an abundance of evidence that it was RNA that had come before DNA, and not DNA before RNA.

1) Biosynthesis DNA is made from RNA.  

2) DNA replication RNA is involved in this process when one might expect it to be unnecessary. DNA polymerase needs to start from a RNA primer bound to the source strand.

3) Protein synthesis RNA -> protein translation involves some additional RNA's, the ribosomal and transfer RNA's. Amino acids are attached to transfer RNA's, which have an "anticodon" end that pairs with the messenger RNA. This pairing and the attachment to the forming protein chain are mediated by ribosomes, which contain both proteins and RNA's. And some experiments suggest that the ribosomes' RNA is their most essential part -- the proteins are assistants.

4) Non-informational "stray" RNA RNA is present in a variety of non-informational contexts, while DNA is never present in such contexts; DNA is exclusively a master-copy molecule.

5) Bits of RNA are found in these enzyme cofactors:

ATP (adenosine triphosphate, the nucleotide with extra phosphates)

NAD (nicotinamide adenine dinucleotide) and NADP (NAD phosphate)

FAD (flavin adenine dinucleotide) and FMN (flavin mononucleotide)

Coenzyme A (contains pantothenate and adenosine)

Cyclic AMP (adenosine monophosphate)

The first four of these are important in biosynthesis and electron-transfer metabolism; cyclic AMP is involved in intracellular signaling.

6) RNA enzymes Ribozymes are enzymes composed of RNA instead of protein.

7) Riboswitches These are bits of RNA that bind with metabolites and provide negative feedback in the form of interfering with the synthesis of enzymes for producing those metabolites, thus being involved in gene regulation. And here also, there is no known DNA counterpart

Answer 5

I believe you are referring to the "RNA World" hypothesis, and that there used to be no such thing as DNA, and all the genetic and cellular processes were catalyzed with RNA.  

I also assume that you don't understand how RNA can come before

DNA since the "central dogma of biology" states that DNA makes RNA which makes protein, therefore you can't have RNA if there was no DNA to begin with.

The hypothesis states that there was a series of cellular mistakes that made deoxy-ribose instead of ribose, (aka the loss of an -OH group at the 2 position of the 5 membered ring) and then since the resulting deoxy form is more stable than RNA, the organisms that had DNA information storage instead of RNA information storage were less susceptible to potentially deadly mutations.  This means that they were "more fit" in the survival of the fittest, and flourished while the RNA only organisms died off.

Here are some things that you may not know about RNA

1. RNA can function as an information storage molecule, almost like DNA.

-There are some viruses that still use RNA as their genetic material just like humans and other organisms use DNA.

2. RNA can function as an Enzyme and catalyze reactions just like proteins can.

-These are called ribozymes and can cut and modify other RNAs.

3. RNA can function as a transfer molecule and helps make proteins and other nucleic acids.  

Answer 6

can you please define the acronyms.  

Based on wikipedia (linked below) it looks like RNA is what makes the protiens and sends signals for DNA, but i really don't know it's over my head.