How does DNA work?

D@vid Asks:

Given that genes aren't the only determining factor in our makeup (we are 50% banana and 98-99% each other), and proteins account for (at least some of) the difference, what factors affect the proteins? are they just a random element? where do they come from? do environmental or genetic factors affect them?

Mitsy Answers:

Hi D@ve...

Yes, you're right there is one body part that does closely resemble a banana, and any guy who claims his body mass to be half "banana" is my kinda.... What?... Oh all right, he never lets me answer anything!

Schpat Resumes:

Sorry about that folks, Mitsy is a young teen who started her life in sex forums, what do you expect! Well now she's pouting so I'll let Mitsy answer a question after I'm finished with this one.

Let me start by correcting you: genes are the only determining factor in our makeup. I'm not throwing decades of nature vs nurture arguments out the window here, but your genes are entirely responsible for the way that your body has developed. Genes are the construction manual for the assembly of the wet and sloppy Mechano Set that is your body! Similarities in DNA between species, like most things, have been highly sensationalised by the mass media. let me quickly explain how they are calculated.

First of all everyone knows that DNA (Deoxyribonucleic Acid) has a "double helixical" structure. In fact this double helix is actually two strands of organic molecules called nucleotides. Each nucleotide on one strand is joined by a hydrogen bond to a nucleotide on the other strand. In Genomics each joining is called a "Base Pair". Genes are made up by patterns of base pairs.

When comparing DNA between different, or even the same, species it is actually the base pairs that are being compared. Now considering that there are only a very small number of nucleotides this really reduces the number of combinations possible and increased the chances of finding pattern matches. By the way the human genome consists of more than 3 billion base pairs, and only about 25000 genes. The number of pairs comprising these genes is accountable for less than 3% of our DNA, the rest has been termed "Junk DNA". Most of the similarities that have been found between us and other organisms are actually found in this "junk". If you did a comparison of relevant genes between humans and chips you'd probably come up with a much, much smaller number.

So why do scientists tout the 98% similarity figure for chimps? Well that's because they are trying to show a common ancestor, and thus prove evolution. Proponents of "intelligent design" (religious folks who have realised that the whole creationism thing is a total croc, but just cant bring themselves to take the next obvious step) say that this proves nothing.

So back to those proteins. Proteins are organic compounds that consist of amino acids joined by peptide bonds. Proteins, much like DNA, are components of cells and are responsible for almost all cellular functions. If DNA is the construction manual for your body, then proteins are the building blocks. DNA is self replicating and, in very basic terms, regulates the manufacture and coding of proteins, that's how it is responsible for how your body is built.

What factors affect proteins? Duh, DNA! What, weren't you listening? Seriously though, while DNA is inherited, in equal parts, from you parents sometimes mutation does occur, this is the basic premise of evolution. DNA is replicated whenever a cell divides, this is done through a complex process of translation and transcription and involves RNS (Ribonucleic Acid). Sometimes however transcription errors occur and DNA gets all messed up. This can cause good or bad things and when happening in the stem cells can be passed on to offspring. When happening in other cells, like skin and lung, it mostly results in cancers. It has been theorised that these transcription errors occur due to environmental factors such as free radicals and stellar radiation from old supernovas, normal radiation will also screw with your DNA.

If you're having a problem visualising all this microscopic stuff then just check out his site. It's very cool!


Ok over to Mitsy..........


Ork Khrist Asks

Why did clicking on these banner ads make me feal so dirty?

Mitsy Answers:

Well Ork, that's because you've only stared doing it. It gets easier with each one. This'll be our little secret! Practice makes perfect.

Thanks Mitsy


The Voice of Dissent:

Er, that would be 'helical', not 'helixical'. How much of this stuff do you paraphrase, and how much is copy/pasted? Or do you do something silly like manually type out everything?

"Now considering that there are only a very small number of nucleotides this really reduces the number of combinations possible and increased the chances of finding pattern matches"
Bollocks. The patterns matched are really really long, more than enough to compensate for the small number (4 in humans, but there are a few weird ones in other organisms) of base pairs. Sure, if you were looking for AGTT, you would find bazillions of matches, but when looking for a set long enough to encode a protein, the chance of finding a random, unrelated match drops dramatically.

Oh, and before anyone goes '4 bases, but they come in pairs so only count as two', switching the order makes a difference, so an AT pair is different to a TA pair.

Synkronos.


Well Synk, stop nit-picking! Yes so I inadvertently made up a new word: "helixical". There, say it seven more times and it might even make it into the dictionary. I think you and everyone else did understand it to mean "helix shaped". So anyway, the protein coding patterns are really long, and it is very easy to find matches if are just comparing base pairs, and yes that is what they did when they found humans to be 50% matches to bananas, and yes that was my point, but thanks for clearing that up! I didn't really go into that too much because it was actually just background into the "what are proteins and stuff for" question?

schpat