#DNA: What’s the Deal?

It’s 2017. We’re three sequels into a massively successful movie franchise about the dangers of science without integrity. Rebooting and endlessly recycling movies doesn’t seem to be a problem, but who cares about that?

Four huge movies about science. Naughty scientists playing God. Evil money hungry corporations sacrificing principles in their endless cancer-like quest for growth.

the_eye_of_mordor_by_sar0n
Grow, my little economy, grow!!!

Nope. Still doesn’t sound familiar? This sounds more like a day on your facebook newsfeed, right?

“Jurassic Park”! At it’s core, this was a tale about the difference between knowledge and wisdom. Scientists who should have known better, and knew the right choice to make ignored it in the quest for money and recognition.

What else was this movie (and it’s progeny) about? Breaking it down into it’s scientific sub-units, “Jurassic Park” was a story about serious genetic engineering. Scientists manipulated and recreated ancient DNA, enabling them to bring back creatures that hadn’t seen the light of day in at least 65 million years. As it turned out, these creatures and the twentieth century didn’t get along so well. The rest you know. If you don’t… watch the movie. On a personal note “Jurassic Park” was one of the last “Oh wow!” movies I saw. The first time that Brachiosaurus appears, it sent shivers down my back.

Remember the scene when DNA was reduced to a friendly cartoon character, something like that old Microsoft paperclip?

clippy-microsofts-talking-paperclip-is-back
Ah, Clippy…

I’m showing my age. Keep reading. Is DNA really that malleable and user friendly? Students and many scientists probably don’t really get the amount of work that went into determining 1): that it exists in the first place, 2): how it works and 3): it’s structure. If you’re this far into this post you most likely have a more than passing interest in science and molecular biology. You know about Rosalind Franklin, Watson, Crick and Wilkins, and various other big hitters in the vast field that is molecular biology.

Like most others I garner things I need to know from textbooks or the internet. All of this information is piled atop older information, blood, sweat and tears. After all of this work, wouldn’t we know enough to be able to create prehistoric GMOs? No. Absolutely not.

One thing that strikes me about DNA, and about life itself, is that within all organisms, across all arenas and Domains of life lies a universal genetic code, evidence of our common ancestry. This code; this cosmic language has given rise to literally all life on this planet. There are a couple of anomalies here and there, but they can be ignored for the sake of this post. Here then, is the Genetic Code:

Adenine, Thymine, Guanine and Cytosine.

…….

You’re tapping your fingers, I know. Your’re waiting for the rest. There isn’t any more. This is the genetic code. Four bases. Often they are reduced to mere letters, and so appear more like a simplistic alphabet. Combinations of these four “letters” comprise the genetic machinery of all life, coding for enzymes, hair, fins, wings, organs, blood vessels, immune systems, bad breath and low IQs.

That’s really it! Four bases, code for all life in all it’s forms. It’s an astonishing feat not only of information storage, but of fidelity of said storage. In nearly four billion years of life on Earth, only 10 percent of the original genetic code has become corrupted, resulting in all life other than simple unicellular organisms. That’s right. Putting it another way, you and me are the result of slight signal degradation. Ten percent doesn’t sound slight! It sounds like a lot! Over 3.5 billion years however, for the original genetic code to degrade only 10 percent is the kind of signal fidelity communications engineers have funky dreams about.

DNAs information storage capabilities are a function of that groovy double helix shape it winds itself into; a result of various molecular bonds inducing this spontaneous double helical twist. A DNA molecule is essentially two molecules; two strands of intertwined de-oxygenated ribose nucleic acid.

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Somewhat resembles a twisted ladder, doesn’t it? Image: Wikimedia Commons

See the “rungs” in the middle of that twisted ladder? They are where the magic happens. These comprise various combinations of the aforementioned bases: Adenine, Thymine, Cytosine and Guanine, joined by hydrogen bonds of varying strength. The bases attach to nucleotides, which are then fused to this sugar-phosphate backbone. In this way they are safely tucked away, wrapped in loving embrace.

The bases don’t just stick together. As mentioned, they are held together by hydrogen bonds of varying strength. Hydrogen bonds are a common chemical bond found in nature. They are quite weak, but form spontaneously when compatible sub units are positioned appropriately. Adenine bonds with Thymine, forming two hydrogen bonds. Cytosine will only pair with Guanine, forming three hydrogen bonds. To repeat, Adenine will only bond with Thymine and Cytosine will only bond with Guanine. This forms the basis of Watson-Crick base pairing, and is the only way bases will pair in DNA. Complementary base pairing is the mechanism by which DNA strands form, and allows new strands to be created later (to be discussed in a future post).

It also makes a pretty neato U-Beaut exam question, and a real gimme if you’re struggling. After all, knowing the above rules: A to T and C to G, you can determine the sequence of a strand of DNA if you have the sequence of it’s opposing or anti-parallel strand.

I won’t ask you to try it!

Future posts will look at DNA replication, including an examination of the mighty ribosome, one of the funkiest biomolecules around. Please feel free to comment on this post and share it with others. See you again- real soon!

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