Spotlight on Science: Molecular Biology

Okay, I know, two biology posts in a row but I am a biologist and it feels like I’ve been neglecting my chosen field I have a degree in this stuff guys I should be able to blog about it without getting distracted by the LHC.

(Actually I keep procrastinating this post by reading about the LHC but let’s just ignore that shall we? Good oh)

So right here today I’m going to talk about the Central Dogma of Molecular Biology, something I view with resentment, anger, and a great deal of love. This is more a history lesson than anything else; in the beginning, everyone thought that proteins were the bits of the cell full of information, mostly because DNA was hella boring.

I would pick one of these to carry my cellular information and it's NOT DNA.
I would pick one of these to carry my cellular information and it’s NOT DNA.

In 1952 , Alfred Hershey and Martha Chase did some experiments using viruses to check this hypothesis out. They had two strains: one with a labelled capsule (proteins) but no DNA, and one with labelled DNA to see what was going on, and which virus survived and infected.

There had been previous experiments in 1944 but this experiment was the nail in the coffin of “proteins are so complex they must carry information yo” school of thought.

Then in 1961, Sydney Brenner, Francois Jacob, and Matthew Meselson showed that mRNA was the thing that shuttled between DNA and proteins, leading us to “DNA makes RNA makes PROTEINS” or this picture here:
Dogma_2

Hold on to your hats though, this is going to take some changing up.

(by the way, non-biology cats, mRNA stands for messenger RNA. There are a bunch of other forms, but I’ll ignore them until I have to mention them)

RNA is twisty as anything and can flick around, bind with itself, with it’s buddies, with whatever it wants basically. If there’s a certain size of double-stranded RNA hanging out, that acts like a sign for it to get degraded. (RNA replication happens too, in viruses) So, RNA CAN AFFECT ITSELF.

Then, when proteins are getting made, they require the help of other proteins to fold or travel. Post-translational modification are changes that happen after the protein is made, by other proteins. All of this can change the information floating around. So, PROTEINS CAN AFFECT PROTEINS.

If we’re looking at AFFECT as not strictly a transfer of information, there are proteins that actively affect the packaging and so the expression of DNA. These can turn genes way up, right down, or off completely. (there are a bunch but an example is histone proteins). So, PROTEINS CAN AFFECT DNA.

Let’s see what we’ve got so far. Dogma_3

Okay, that’s decent. Of course, DNA replicates and that’s a transfer of information so DNA AFFECTS DNA.

Reverse transcription is where RNA can be used to create DNA, either as part of viral shenanigans, or some transposons (“jumping genes” – there’s some transposon chat here), or just when scientists are using it for their own nefarious purposes – transfer of information, RNA AFFECTS DNA.

(there are cases where DNA has been seen to go straight to protein but that’s never been seen within a cell, so I’m going to act like it doesn’t happen.)

Right, it looks like we’re done:

Dogma_4

In it’s essence, the Central Dogma is how information passes from one thing in our cells to other things in our cells. (DNA, RNA, and protein). As we discover more and more about how all these pieces work, it can be summarized as being “not that simple” – are modifications to how much protein is produced changes in information?

Perhaps not at the cellular level, as they don’t affect the base sequence of the protein, but they can have serious large-scale effects (cancer, obesity, and type II diabetes to name a few).

The idea that we can distil molecular biology to something as simple as a triangular graph isn’t… wrong, persay, because it is a central dogma, but it is misleadingly simplistic. The central dogma I used to write over all my second and third-year books was “Cells are crazy complex, and genes are no better.”

Dogma_5

Further reading:


I mean you could just do a genetics degree but otherwise I actually advise wikipedia as being the place to start. Many of the articles written on things like epigenetics, RNA replication, and prions get bogged down in technical language PDQ. Of course, if you want a blog post on any of this stuff, I’m a dab hand at turning technical chat into phrases like “technical chat”. This site will help you with epigenetics but you do need a bit of a biology background.

Seriously just ask me, I don’t bite.

– Sophia, who really doesn’t bite, I promise.

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