Bill Bryson - The Stuff of Life

Every living thing is an elaboration on a single blueprint. This blueprint is called DNA (deoxyribonucleic acid).

DNA was first discovered back in 1869 by Johann Friedrich Miescher, a Swiss scientist working at the University of Tubingen in Germany. While searching microscopically through the pus in surgical bandages he found a substance he didn’t recognize and called it nuclein (because it was found in the nucleus of cells).

As far as anyone could tell DNA didn’t do anything at all. But there were two problems with dismissing it. Firstly there was nearly 2 meters of it in nearly every nucleus and secondly the fact that it kept turning up, like the suspect in a murder mystery. DNA appeared clearly in two particular studies – one involving the Pneumoncoccus bacterium and another involving bacteriophages (viruses that infect bacteria). The evidence found here suggested that DNA was somehow involved in the making of proteins, a process vital to life. Yet it was also clear the proteins were being made outside the nucleus, away from the DNA. No one knew how DNA could possibly be getting messages to the proteins. The answer is RNA (ribonucleic acid) which acts as an interpreter between the two.

DNA is made up of four basic components called nucleotides – adenine, thiamine guanine and cytosine. Every living thing is a variation of these four components but every now and then, about one time in a million, a letter joins in the wrong place. This is called SNP (single nucleotide polymorphism) more commonly known as ‘Snip’. These variations or ‘snips’ get passed down through generations and make us different from each other. ‘Snips’ can sometimes leave you vulnerable to diseases, but they could also give you an advantage e.g. increased production of red blood cells for someone living at high altitude.

It was first thought that humans had at least one hundred thousand genes, but that number was drastically reduced by the first results of the Human Genome projects, which suggested a figure more like 35 to 40 thousand genes, about the same number found in grass. Interestingly almost half of human genes, the largest proportion known in any organism, don’t do anything at all, except reproduce themselves.  

In some sense we are all slaves to our genes.

Ainslie