Almost everyone has heard of DNA - deoxyribonucleic acid.
It is the stuff of genetics. The grand plan inside each cell which controls everything.
The driver behind evolution and natural selection. Present in every living thing on or in the planet.
It is both a simple molecule and very complex.
The simplicity comes from being composed of only four bases (adenine, thymine, cytosine, and guanine), a sugar (deoxyribose), and a phosphate linker.
Chemically, it is not particularly difficult to make and polymers of DNA can be readily synthesized in an undergraduate lab. Indeed, for a long time, it was thought DNA was too simple to be the basis for genetics.
Its complexity arises from putting the bases together in a long string millions of bases long.
Each triplet - for example, a thymine, thymine, and cytosine - spells out the instructions for a specific amino acid.
With four possible letters in each of three possible spots, a total of 64 codons can be crafted which is more than enough to code for the 20 amino acids required to make proteins and still have a few codons leftover which say "stop."
But DNA is a relatively recent discovery.
For the longest time, people didn't understand the basis for heredity.
That cows produce cows or corn gives rise to corn was understood. It is the basis for our modern agriculture. But why a brown cow might produce a white calf or how some corn would have different coloured kernels was not well understood.
For the most part, our ancestors were breeding animals and crops based on phenotypes - the observable characteristics or traits of an organism.
A big cow mated to a big bull tended to produce bigger babies. Different strains of corn, when cross fertilized, produced bigger ears.
We have been genetically manipulating our food supply for 10,000 years although without much understanding of what we were doing or how it worked.
Our modern understanding of genetics is generally considered to have started with the work of Johann Gregor Mendel. In 1852, he began a decades long experiment to try to under how traits were passed from parents to offspring.
He began his research on mice but switched to honey bees and plants. His more famous work arises from his study of garden peas.
He demonstrated the presence of an inheritable factor which passed from parents to offspring with each parent contributing part of the code.
His results began a search for the molecule of inheritance which ended in the 1950s when Watson and Crick announced their structure for the double helix and determined the biochemical basis for genetics.
Since the 1950s, many advances in genetics have occurred.
To a large degree, they have depended on brilliant insight and lots of late nights slogging over newly crafted instrumentation and techniques.
Science is not easy, but it does enlighten.
By the 1990s, biochemists were in the position where they could finally decode the human genome. They could read all
2.9 billion base pairs which make up our chromosomes.
To put that in perspective,
2.9 billion letters at an average of six letters per word would give 480 million words or about 10,000 typical-length novels. It is a lot of information.
Deciphering the human genome is one of great accomplishments in science. And it didn't stop with just humans.
Many different organisms have now had their genomes sequenced.
We now have the blueprints for everything from chickens to spruce trees.
There have been many surprises along the way, not the least of which is how few genes are found in our DNA. It is typically given as around 30,000 while something as simple as yeast have 6,000 genes. There was always an implicit assumption that complex organisms, such as us, would have way more genes than simple single cellular species.
In 2004, scientists made another astounding discovery. There are 481 stretches of DNA found to be conserved across an amazing number of organisms.
This is similar to finding out every book in the world has 481 identical passages in them.
This would make sense if these conserved areas were genes coding for particularly important proteins or manifesting as necessary phenotypes but as far as anyone could tell, they were simply stretches of DNA which all organisms possessed.
That is, until a paper published last week presented the results from a study of one particular set of conserved DNA.
The authors found deleting these base pairs doesn't kill an organism but it does affect the morphology of the tissue in certain parts of the animal.
In the case of this study, it is the brain.
We understand much about DNA. We have come a long way since the early days of genetics and inheritance. But it is clear we still have a long way to go in understanding the very core of our being.
