by Hazel Anna Rogers
Intro by Carl Kruse
Every year we take some time to celebrate that moment on 25 April 1953 when Crick and Watson issued their findings on the structure of DNA, and of the benefits to humanity that such knowledge has wrought. Our previous celebrations of DNA Day on the blog are here and here and this year we join again with all those with some nerd in their soul to celebrate DNA Day.
Our friend and resident writer Hazel Anna Rogers gives us a quick background on events leading up to that momentous day in 1953 that changed history. Take it Hazel!
How DNA was Discovered
In 1869, chemist Friedrich Miescher was deep into his studies of human white blood cell nuclei when he came across a certain group of protein components within the cells that he wanted to isolate and study. His aim? To find out exactly WHAT proteins they were. So he decided to order sheer quantities of used bandages from a clinic near` his home in Switzerland so he could separate out the leukocytes (white blood cells) and delve further into their structure.
What he discovered was unlike anything he’d seen before.
Within the nuclei of the cells, he found a strange matter that was both resilient against the digestion of proteins AND consisted of high levels of phosphorous (much greater than any proteins that Miescher knew of). He identified this new substance as ‘nuclein’ or ‘nucleic acid’, though in time it became more widely known as ‘deoxyribonucleic acid’ which was abbreviated to DNA.
This incredible breakthrough was ignored by science for many years, even though the finding was clearly attributable to only him, unlike other findings such as the discoveries of lipids, proteins, etcetera.
Many scientists after Miescher attempted to understand how this ‘DNA’ was organized within the space of the cell, and how it was combined with the other cell components. Phoebus Levene, a Russian-born chemist of the early 20th century, (who was previously a pharmacist) managed to order the nucleotide (the molecule that acts as the building block of both RNA and DNA, as well as being important in metabolization, the signalling of cells, and the reactions of enzymes) into its main three components: a phosphate group, 5-carbon sugar, and a nitrogenous base. Therefore, Levene was the first scientist to accurately suggest how the molecules of DNA (and RNA) might be composed.
Phoebus Levene. Photo: Rockefeller University.
After Levene came Erwin Chargaff, a biochemist from Austria working in the 1950s, who came to the conclusion that the formulation of DNA, according to its composition of nucleotides, is different is all animal species. He also propounded that the order of these nucleotides is different in most cases of DNA (contrary to Levene’s proposition that they always maintain the same order), but that the properties of pretty much all DNA is the same, despite the levels of each separate component being slightly different.
Erwin Chargaff, 1930. Photo: Brain Pickings.
Now we come to Rosalind Franklin, who, similar to Levene, has often been forgotten by science. Her and Maurice Wilkin’s integral work on X-ray crystallography were vital to the infamous discoveries Watson and Crick in the early 1950s. James Watson, an American biologist, and Francis Crick, an English physicist, came together to work on the 3-D model of DNA. From their work, we now have the double-helical DNA structural model that we all know and understand as an accurate visual representation of DNA. The two men worked tirelessly cutting out endless pieces of cardboard to figure out DNA shape, and puzzled about how to arrange the modules to find the perfect fit. Finally, it came to them (albeit with the help of scientist Jerry Donohue), that with a shift in the configuration of the atoms of the models, they would be able to seamlessly recreate a concrete version of what they knew to be true from the discoveries of the earlier scientists. And so the DNA spiral (which I’m sure you have in your head right now) was born.
Rosalind Franklin, Photo: Sciencemag,org
And there we have it! A brief(ish) summary of all the discoveries that led to the greater understanding of what DNA really is. But…what actually is DNA? Did you really pay attention in all those science lessons?
Here’s a simplified explanation of DNA, just in case you were asleep through chemistry:
DNA consists of two strands of a double-stranded helix that are held together by hydrogen bonds.
A (or adenine) is ALWAYS in a pair with T (thymine), and C (cytosine) is always paired with G (guanine), all in varying amounts, but with proportions that remain the same in the DNA of all living things.
Almost all DNA double-helixes are right-handed, which basically means that they can be represented with a right hand: so, if you point your thumb to the sky and curl your fingers around it, the thumb would be the helix’ axis and the fingers would be the sugar-phosphate backbone of the DNA.
The outer edges of the base of the DNA, which contains nitrogen, are exposed so that they can bond with hydrogen around the cell, which makes DNA accessible for additional molecules such as proteins (essential for helping to express DNA and replicate that DNA throughout the body).
So…still no clearer? I thought not.
Well, why should you care about DNA anyway? Why is it so important, and why did all these scientist work so hard to try and understand it?
As you probably know, DNA is completely unique to each individual. It contains within it all the information required to maintain our bodies, and to build and grow it all the way from conception until death. From advancements in our understanding of DNA, we’ve managed to discover minor variations within the DNA model that Watson and Crick proposed that have led to breakthroughs in recognizing illnesses, deficiencies, and disorders. These include identifying Down syndrome and detecting predispositions for Alzheimer’s disease, Huntington’s disease, and other degenerative diseases of the mind, as well as certain cancers.
If you got your own DNA looked at, you might find out all sorts of interesting things about your own body, including your levels of immunity, the health of your mind, the health of your heart, lungs, and bones. You could even find answers about how you could fight the course of aging, and what you should eat to be at optimal health!
More than anything, DNA teaches us how very different we all are. With our knowledge of DNA and genetics, how could we possibly think that one diet could make us all lose weight, or that one form of exercise could be effective for everyone to be healthy and fit? I hope you’ve learned something from this article, and, on this National DNA Day, maybe you’ll think to raise a toast to the scientists who have helped us to understand the wondrous human body better.
(Most information on the discovery of DNA at https://www.nature.com/scitable/topicpage/discovery-of-dna-structure-and-function-watson-397/)
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Other posts by Hazeal Anna Rogers were on the Spring Equinox and on Micro-bakeries.
The blog’s last post discussed Stoicism.