Revision of the "Central Dogma" of Molecular Biology

New year, new content!

Or rather... old content wrapped up with a shiny new "BIOC2001" label in the case of this post.

This semester I'm taking ANHB2212 (Human Structure and Development), PHAR2210 (Foundations of Pharmacology), PHYl2001 (Physiology of Human Body Systems) and BIOC2001 (Biochemistry and Molecular Biology of the Cell). Stay tuned for hearing more on all four units, if time and motivation permit!

Without further ado, let's get stuck into the first lecture for BIOC2001 (simply because that's the first one that I have an online test for... or at least I think I'm meant to be having an online test for but they haven't said anything). Most of this is just revision, so I'll be linking to the relevant posts.

Outline the central dogma

I'm just going to copy-paste an earlier post on this one: "I'm sure you probably know this by now- DNA gets transcribed to mRNA, mRNA gets translated into protein, yada yada yada." (Yup, I'm so lazy that I couldn't even be bothered trawling through to find an actual description.)

(Actually, I just stumbled across one serendipitously while finding links for the other sections. In my post on DNA structure, I wrote "The central dogma is simply the process in which DNA is transcribed into mRNA, which is then translated into protein." Same shit really.)

Describe the structure of DNA & RNA 

See my previous posts:

DNA Structure
Nucleic Acids- Properties of RNA

Outline mechanism of DNA replication 

DNA Replication

Compare & contrast transcription & translation in prokaryotes & eukaryotes

I don't appear to have covered this before, so I might actually have to write something new. Ugh. Anyway, most of the general processes are similar between prokaryotes and eukaryotes: RNA polymerase creates mRNA which is translated on ribosomes to form protein. However, there are some important differences.

The main differences involve timing and location of the two processes. In prokaryotes, since DNA is just floating around in the cytosol, both transcription and translation can occur simultaneously in the cytosol (translation occurs as the DNA is transcribed). In eukaryotes, however, transcription occurs in the nucleus, and then the mRNA goes to the cytosol where it is translated. Since the transcript obviously can't be in the nucleus and the cytosol at the same time, the two processes are not simultaneous in eukaryotes.

A more subtle difference between the two is the type of ribosome that is used. Eukaryotic ribosomes are bigger than prokaryotic ribosomes- 80S as opposed to 70S. (Not 100% sure what "S" stands for but it has something to do with sedimentation. Most important thing here is larger S = bigger ribosomes).

Yet another subtle difference is that the initial amino acid in translation is formylmethionine in prokaryotes, as opposed to plain old methionine in eukaryotes. Not sure what the significance of this is though.

Hmm... what else? Oh yes, there's a "Shine Dalgarno" sequence on prokaryotic DNA, which is where ribosomes attach to and begin translating. I don't think there's anything entirely analogous in eukaryotes. Instead there's a "Kozak sequence," which to my understanding isn't really a binding site, but rather acts to enhance the initiation of translation. The Kozak sequence can vary slightly, and its variations can affect how readily translation is initiated.

Describe the genetic code and its characteristic features

See Translation- Part 1.

Describe a general outline for the process of translation and the sequence features that control its initiation and termination

Translation- Part 1
Translation- Part 2