August 03, 2010

Sunburn

June 18th, 2010


It has been a long, long time since I last had a day off without worrying about work. Since I last sat out in the sun with a glass of wine and enjoyed the company of some of my good friends, and since I could fully relax knowing that, for the first time in three years, I actually have nothing to do. It’s a strange feeling, let me tell you. After our final lecture today, some of my good friends and I went to sit on the grass to enjoy the sun. After trooping round campus for a good while, trying to find a spot of grass minus the duck poo (!), we finally settled by the lake and enjoyed what may well have been our last afternoon together. By everyone else’s accounts, it has been a glorious day; blazing sunshine, baking hot, and not a cloud in the sky.

Hrumph. I don’t like summer very much. Hayfever, exams (usually), uncomfortable, hot, sticky, sleepless nights...no, summer is not my favourite time of year. Every year I TRY and like summer – I always think, ooh, it’s summer, it’s gunna be good this year. It never is.

One of my major problems with summertime is this: my skin is so fair that ten minutes in the midday sun is enough to turn me BRIGHT RED, and make me curse the sun even more than I already do. I can hear you all saying, “well if you’d only wear suncream, you wouldn’t get burnt”. Well, I have given up on suncream – it doesn’t seem to work for me unless it’s AT LEAST factor 50, and that’s both difficult to find and very expensive. I usually just cover my shoulders and wear tights throughout summer instead.
Today was no different, although there must have been about 15 minutes this afternoon where I was so hot that I simply had to remove the cardigan covering my shoulders. I’m paying dearly for this moment of foolishness, and am bitterly wishing that I’d paid attention to the voice of reason in my head that told me that it was a bad idea at the time.

They say that sunburn is really bad for you; that it’s a cause of cancer, and that even getting burned once has lasting damage, blah blah blah. Well, I don’t like scaremongers in general – in fact, I am one of their biggest critics – but it is true that sunburn is exceedingly bad for you. Let me tell you why.


Every cell in your body contains DNA. Most people know that DNA contains the “genetic information” for an individual, but what does this actually mean? Virtually every function that your body carries out is carried out or controlled at some level by proteins. I honestly can’t think of ANYTHING in the human body... (now you’ve got me thinking)... no, really, can’t think of anything that doesn’t involve proteins at some level.

Haemoglobin: the molecule that makes blood red and carries oxygen round your body – that’s a protein. All the digestive enzymes – they’re proteins. Insulin: the hormone that keeps your blood sugar constant – that’s a protein. The light-sensing units in your eyes – they’re proteins. Neurotransmitters, muscles, hair, fingernails... need I go on? I think you get the picture. But back to my point, DNA is a code which contains all of the information needed to MAKE these proteins.

DNA is a quite complicated molecule, but essentially it’s got a backbone made of a type of sugar and a chemical group known as a phosphate group. Attached to this backbone are BASES, and this is where the information is encoded. There are four bases: A, T, C and G, and it is the sequence of these bases which is the code.

Now, many of you will know that proteins are long strings of individual units called amino acids. Simply, how the genetic code works is that the machinery that makes proteins “reads” along the DNA molecule, and puts the right amino acid into the protein that’s being made, according to what is encoded in the DNA.

Let me explain this a bit further.
I’ve got a DNA molecule, and its sequence of bases is GATAGTAAGCCATCACGT. Now, the protein factory reads this in groups of threes: GAT-AGT-AAG-CCA-TCA-CGT. Each of those groups of threes codes for one amino acid. So, that sequence in the DNA will translate into a protein that might be something like this: Ala-Gly-Leu-His-Tyr-Trp. I have no idea what it actually is – I’d have to look it up – but do you get the idea? Then, it is the chemical properties of the amino acids themselves that makes all the different proteins do different things.

Now, what I have just described to you is the central dogma of molecular biology. It is the most fundamental, absolutely basic, elementary function of all life on earth; the ability to translate DNA code into protein.

So how does all this relate to my roasted shoulders? Why did I bother telling you all that stuff?
Well, in light of what I just said about how essential proteins are, and how all proteins are made from DNA code... imagine how catastrophic it might be if that DNA got damaged.

Think of this as like me building a Lego model using an instruction manual. If someone rips out a page, or scrambles up all my pages, or scribbles in them, or adds in a page that shouldn’t be there, then I’m going to get confused and I’m just not going to be able to make the model the way it should be. This is the same with DNA and protein: if DNA is damaged in some way, then the protein that’s made from it just won’t be what it should be, and it might not work properly.

So many human diseases are caused by exactly that; damage to DNA causing non-functional proteins to be made. Skin cancer is the one that everyone knows about with regard to sunburn, so let me concentrate on that.

Sunlight contains ultraviolet radiation, which is just a very high frequency type of electromagnetic wave. Now, because it is high frequency, it has a lot of energy – far more than those poor atoms in the DNA in your skin cells, so when UV rays hit them, it actually makes the atoms behave in a different way. Now, this becomes a massive problem when two T bases or C bases are adjacent to each other in the DNA sequence (TT or CC). This high energy from UV light causes them to physically fuse together, to create a weird molecule that is never usually found in DNA. Now, the machinery that reads the DNA simply can’t read this molecule – it just doesn’t recognise it.

Going back to my Lego analogy, if someone stuck a page into my instruction manual that was written in Chinese, I would be completely stumped. I just wouldn’t understand what I was supposed to do. So what could I do? I could throw my hands up and say, “I give up”, or I could take a wild guess at something and just add in a piece to my model at random. This is what the cell does; often, the DNA damage is so severe that the cell will just give up, or it will add in an amino acid at random (a mis-read, rather than a non-read). Either way, the protein gets screwed up.

...But what if that protein was really important in controlling cell division? What if that protein was absolutely essential in making sure that cells don’t divide when they shouldn’t do? What if the cell absolutely couldn’t do without it...? Cancer is just that; when the proteins that control cell division get screwed up because of underlying DNA damage.

Imagine that I am sitting in a little booth by the side of a busy junction, manually controlling the traffic lights. My job is to change the lights at the right time to make sure that the junction keeps working properly and that there are no accidents. Imagine then, if some very mean person comes into my booth and ties me up. I wouldn’t be able to perform my duties properly, and the state of traffic at the junction would disintegrate into pandemonium. Imagine what chaos could be caused, and how catastrophic may be the consequences. Well, it is the same in the cell. If cells just divide uncontrollably, then you get a lump – a tumour – and this can have disastrous effects on neighbouring cells, and can completely disrupt the way that that tissue works. This is why cancer is so devastating – because these cancerous cells just keep dividing and dividing and dividing out of control until they physically disrupt surrounding tissues. Bad stuff.

So let me bring all this together. All the while I was so foolishly sitting out in the sun all exposed earlier on, those ultraviolet rays from the sun were beating down on my unsuspecting shoulders and causing the bases of the DNA in my skin cells to become damaged. The machinery that reads my DNA and translates it into proteins simply can’t read this – “it may as well be written in Chinese!”, and subsequently can’t make the proteins the way they should be made. If I were unlucky enough to have this damage happen in the parts of DNA that encode cell division genes, then maybe the control of cell division might be lost and I’d end up with skin cancer. Make sense?

That’s a pretty scary thought, huh? I thought so. But like I said earlier, I hate scaremongering, so let me ALSO tell you that a skin cancer will not develop just from one bout of sunburn. Why? Because, as all you faithful readers of my previous notes might be beginning to appreciate, cells are BLOODY COMPLICATED!! There is never such a thing as *ONE* protein that controls cell division – there are several. There are some back-up mechanisms, and many levels of control. Cancers develop following inactivation of all of these mechanisms through lots of cumulative DNA mutations. Ever wondered why cancers are generally a disease of old age? It simply takes time for these mutations to accumulate.
Nonetheless, one bout of sunburn may indeed have contributed one to these mutations – I might have lost one of my nine oncological lives! So it’s best to stay covered up in the sun if you’re fair skinned – even 15 minutes is enough! I’m going to go to bed now, and rub moisturiser into my sore and sorry-looking shoulders. Hrumphh. Summertime.

Just as a heads up, Cannon Park Tesco’s sells factor 50 suncream ;-)


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