This week, Everyday Einstein begins looking at how proteins are made and what they're good for. We start at the source of all proteins: DNA.
RNA vs. DNA
RNA is lot like DNA, in that they both are made of a bunch of nucleotides stuck together. However there are a couple of key differences. First, one starts with “R,” and the other starts with “D.” This might sound like a dumb thing to say, but all of the rest of the differences in the two molecules can be traced back to this fact.
The “D” of DNA stands for “Deoxyribose,” whereas the “R” of RNA stands for plain old ribose. Let’s use our strategy of tearing apart big words to see what the difference is between these two.
Back in the 19th century, scientists isolated an interesting compound from gum arabic (a gummy sap that comes from the acacia tree). They called it arabinose. When a biological word ends in “ose,” that usually means it's a kind of sugar (like fructose, sucrose, glucose, etc.). The “arabin” part comes from the fact that it was found in gum arabic.
Over time, scientists discovered that there were a few different kinds of this type of sugar, depending on which way you arranged the atoms. One of those kinds they called “ribose,” which is just a shortened version of arabinose.
So now that we know more about ribose (the “R” in RNA), let’s take a look at deoxyribose, the “D” in DNA. Deoxyribose is ribose that’s been “deoxyied.” In science, words that start with “de” usually mean remove, and “oxy” almost always refers to oxygen. So “deoxy” means, remove an oxygen.
Putting that all together, deoxyribose means a ribose with an oxygen removed.
One of These Nucleotides Is Not Like the Other
As I mentioned earlier, one more important difference between RNA and DNA is found in the kind of nucleotides that RNA uses. While DNA uses Guanine, Adenine, Thiamine, and Cytosine (G, A, T, and C); RNA uses Guanine, Adenine, Uracil, and Cytosine (G, A, U, and C).
And now the reason for this is....nobody knows for sure!
However there are several possible reasons. One of the most likely is that Thymine is more stable. Since DNA is responsible for the long-term storage of your genetic code, stability is pretty important. RNA on the other hand, tends to only stick around until its job is done, so stability is less important.
So now you know more about the differences between DNA and RNA. Next time we’ll take a look at how your cells use RNA to make the workhorse of biology, the protein.
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