reply to post by Night Star
Radiation comes in 3 forms, alpha, beta and gamma.
Alpha (a) radiation is very short range (~10cm in air) and is extremely ionising. It is very harmful to whatever it touches, fortunately, it can do
very little damage due to its short range and the fact that it's absorbed very easily. If you held an a source in your hand, it would burn your skin
but do little else. If you swallowed an a source, you'd be in a bad situation.
Beta (b) radiation is short range (~1m in air) and is moderately ionising. It is quite harmful to whatever it touches, it is arguably the most
dangerous type due to its penetration, range and ionisation factor, but in reality depending on the situation, a or y radiation will be more harmful.
It can be fully absorbed by a thin sheet of aluminium or similar.
Gamma (y) radiation has a near infinite range in air and is very hard to stop. It requires very thick lead and concrete to absorb it. Its extreme
penetration power is due to the fact that it is unlikely to ionise whatever it is passing through at the time, compared to other types of
Basically, if you were in a room full of radiation, you'd want it to be a, while y would be the most dangerous. If you swallowed some radioactive
rocks, you'd want them to be y, while a would be the most dangerous.
The radiation used in the treatment of cancer is y, because the aim is to provide a controlled dose of radiation at a specific place within your body.
Unfortunately, due to the nature of radiation we can't ensure that the entire dose is absorbed at the tumour site, so we use low-ionising gamma rays
(technically x rays, but the semantics of that change weekly, the physics community is so pedantic).
Before I go on, I have to explain cell replication. Your body has trillions of tiny bubbles of stuff called cells, with each cell performing a
specific function, you have muscle cells, nerve cells, skin cells and so on. Some cells in your body are quite short lived, so they need to make
copies of themselves to maintain the functions of your body before they die (not all cells do this, notably your brain cells). To do this, they
undergo a process called mitosis, the end result of which is 2 cells instead of 1.
During mitosis, everything in a cell is duplicated so the daughter cell is a perfect clone of the cell before, however, the DNA duplication process is
a risky business. DNA is stored during normal operations as a kind of twisted ladder, like this -
where A can only pair with T and C can only pair with G, but you can have either base on either side of the ladder. During mitosis, the DNA is broken
down the middle so it looks like this -
there 2 separate strands are surrounded by single bases floating around that look like this
|A |A |C |A |T |G and so on
these floating bases then join to their complementary pairs in order to form 2 separate but complete strands of DNA so this
turns in to this
This process can go wrong however, resulting in mutation - it's the reason people today all look different and we're not all single celled
Mutation in humans is a slow process, our cells divide quite slowly and our DNA is so well protected that mutation is rare, and when it does happen
it's often inconsequential due to the way our body processes DNA.
If you add ionising radiation in to the mix, DNA mutation becomes a much more frequent occurrence during mitosis, which will most likely result in
The use of radiation to treat cancer works on a very simple concept - tumour cells replicate faster than normal cells, therefore they will be more
damaged by a certain dose of radiation than the rest of our body's cells will be. The idea is that we kill a lot of them and only a few of us, and if
we keep doing that, eventually they will have nothing left.
This obviously doesn't always work out as planned, there is a lot of random chance involved. If we just happen to destroy the tumour suppressing gene
in one of our healthy cells, or even damage the DNA in such a way that one more mutation will destroy it, we've created another cancer which can be
more dangerous than the first, the way DNA codons work is that they're redundant, TAG can be the same as TAC and TAT and so on, but even if we change
a codon to code for something else instead of what it's supposed to, it might not have any effect, if TAG, TAC and TAT code for a certain amino acid
and CAG codes for another, changing the codon to CAG might make us produce the second acid instead, but that might not mean anything.
I've gone on and on and I'm at the limit, I'll happily explain everything in more detail if anyone's interested, but I don't like to do more than