Dedicated detection

Small, icy rooms without heating and English pubs where a lot of alcohol is flowing are ingredients not only for many exciting detective stories, but also for the story of the discovery of the DNA molecule.

DNA stands for deoxyribonucleic acid. But you can immediately forget that awfully difficult name. Just remember that the DNA molecule contains our hereditary information and through the DNA molecule it is possible to investigate everything related to heredity.

Moravian scientist Gregor Mendel, the father of genetics, conducted experiments on pea plants in the 19th century to find out more about the rules of heredity. (© Bill Ebbesen - Wikipedia)

Moravian scientist Gregor Mendel, the father of genetics, conducted experiments on pea plants in the 19th century to find out more about the rules of heredity. (© Bill Ebbesen – Wikipedia)

The existence of the DNA molecule had already been discovered at the end of the 19th century. In the first half of the 20th century, it became clear DNA contains genetic information and thus plays a part in heredity. But how the molecule is built was learned only much later.

In his book The Double Helix, the American biologist James Watson describes the quest for the structure of DNA.

“Science seldom proceeds in the straightforward logical manner imagined by outsiders”, he writes. “Instead, its steps forward (and sometimes backward) are often very human events in which personalities and cultural traditions play major roles.”
The find was not at all like the happy moment of the Greek philosopher Archimedes who more than two thousand years ago, while sitting in a bath tub, all of a sudden came up with the solution to a physics problem and exclaimed: “Eureka” (I have found it).

Obsessive
On the contrary, the discovery of the structure of DNA took two years of obsessiveness at the beginning of the fifties in the last century. Watson was working with Francis Crick at the University of Cambridge in England. Many lunches were dedicated to discussions about the structure of DNA. Ideas cropped up and could then be thrown into the waste paper bin. Watson recounts fantastic theories, scribbling on old newspapers and at a later stage the building of all kinds of possible models of the molecule.

Watson testifies to the fact that scientific research requires endurance and hardship.
“Back in my rooms I lit the coal fire, knowing there was no chance that the sight of my breath would disappear before I was ready for bed. With my fingers too cold to write legibly I huddled next to the fireplace, daydreaming about how several DNA chains could fold together in a pretty and hopefully scientific way.”

Discoverers of the structure of DNA Francis Crick (right) and James Watson (middle) with American geneticist Maclyn McCarty. (© Marjorie McCarty - Wikipedia)

Discoverers of the structure of DNA Francis Crick (right) and James Watson (middle) with American geneticist Maclyn McCarty. (© Marjorie McCarty – Wikipedia)

At the time, just after World War II, there was general acceptance that genes were special types of protein molecules. But, writes Watson: “Experiments strongly suggested that future experiments would show that all genes were composed of DNA. If true, this meant to Francis that proteins would not be the Rosetta stone for unraveling the true secret of life. Instead, DNA would have to provide the key to enable us to find out how genes determined, among other characteristics, the color of our hair, our eyes, most likely our comparative intelligence, and maybe even our potential to amuse others.”

Nobel Prize
Serious and hard work, with an endless devotion to unveil the mystery, finally resulted in the only possible solution for the structure of DNA. Watson and Crick showed DNA has the structure of a double helix. On April 2, 1953, the manuscript telling of the discovery went off to the editors of the magazine Nature.

In 1962, Watson and Crick together with their colleague Maurice Wilkins received the Nobel Prize for Physiology or Medicine for their discovery. We still had to wait until the eighties before the structure of the DNA molecule could actually be verified with advanced research equipment and confirmed with a photograph.

By discovering the structure of the DNA molecule, science made a giant leap forward. As of that moment, researchers could begin to unravel how DNA operates.

DNA is one of the four molecules of life, indispensable for the creation of life. DNA and its related nucleic acid RNA are responsible for reproduction. The other molecules of life are proteins that help molecules bond with each other and thus form larger entities; carbohydrates that provide fuel support; and lipids, molecules that don’t dissolve in water and serve as cell membranes to separate cells from their environment.

Ladder
Of course, this fascinating story isn’t complete without at least a broad outline of what DNA is and does. Here the story becomes complicated, but I’ll try to keep it as simple as possible. DNA consists of a string of basic building blocks called nucleotides. Every nucleotide contains three smaller molecules: a phosphate, a sugar, and a base. Two strings of nucleotides together make up some kind of ladder. The phosphates and the sugars are the stiles of the ladder.

A sketch of the structure of an RNA molecule. (© BruceBlaus – Wikipedia)

A sketch of the structure of an RNA molecule. (© BruceBlaus – Wikipedia)

The bases of the two opposite nucleotides bond together and form the steps of the ladder. These base pairs contain the genetic code. The genetic code is all the information a cell needs to reproduce itself and run its chemical factories. Make the ladder twist continuously and you end up with the DNA molecule.

DNA has no use without RNA, which stands for ribonucleic acid. The structure of RNA consists of only half of the ladder: one stile with bases sticking out. RNA plays a critical role in transferring and reading genetic messages, which results in the production of proteins. New research focuses on special RNA molecules, made in the lab. They are potent new drugs that can silence a disease-causing gene.

Similar
Every human cell holds 23 pairs of chromosomes. Half of them originate from your father, the other half comes from your mother. A chromosome is made up of one very long DNA molecule. Different parts of DNA have different tasks, some of which are not known yet.

The segments of DNA that contain hereditary information are called genes. Many genes can fit along the ladder of a single DNA molecule. The human genome comprises around 20.000 genes, according to the latest view among scientists worldwide. It contains about three billion letters of code, the combination of bases along the double helix ladder of DNA.

Chimpanzees and humans share more than 98 percent of their DNA. (© cheekylorns - Fotolia.com)

Chimpanzees and humans share more than 98 percent of their DNA. (© cheekylorns – Fotolia.com)

The difference between the genome of two human beings is only about 0.1 percent, being about three million letters. The difference between the genome of a human being and of a chimpanzee is 1.5 percent, being about 45 million letters. This makes the chimpanzee more similar to the human than to the gorilla.

It is like writing different books using the same set of words in a different pattern and order, according to science writer Matt Ridley. You don’t need new words to write a completely different book.

Image

Detective © Malchev – Fotolia.com
The structure of DNA © hi_def_animation – Fotolia.com

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