Our governing molecules, from concept to a structure

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A child is a mix of two parents. Gregor Mendel (1822-1884) questioned this belief, and in 1865 he demonstrated that expressed traits are not a mix. Instead, traits are either “dominant” or “recessive”. An inherited dominant trait is invariably expressed. On the other hand, a recessive trait is expressed only when the dominant one is missing. Mendel laid out principles of inheritance, while experimenting on common-pea plants. He was unaware about governing molecules behind these traits, and simply called them “factors”.

Most scientists in Mendel’s time ignored his findings. Many decades later, we re-discovered these principles. In 1902, Walter Sutton an American biologist and Theodor Boveri a German zoologist independently developed the chromosome theory of inheritance. They proposed that Mendelian”factors” or “traits” may be located in a special area of a cell. This area probably was chromatin. Many scientists of the day debated these theories. Meanwhile in 1909, Danish botanist Wilhelm Johannsen coined the word gene.

X-rays, molecular structures and Chromosomes

In 1898 Wilhelm Roetgen discovered X-rays. This discovery also paved way for crystallography – A science to visualise structures of molecules. Max von Laue, and Lawrence Bragg discovered the power of X-rays to identify tiny structures. Both earned Nobel Prize in 1914 and 1915 respectively. Over next few years, scientists could make sense of unseen structures and tiny proteins in human body.

In parallel to these developments, Thomas Morgan (1866-1945), an American Biologist was doing research on inherited traits. Unlike Mendel, he choose drosophila, an insect with a short life span. He could replicate Mendel’s work. Later, he proposed that chromosomes contain “genes”, “traits” or “factors”. He earned 1933 Nobel Prize in Medicine for his work. The same year, Ernst Ruska (1906-1988) a German physicist had build a first electron microscope. Many unseen structures inside a cell, including chromosomes, were now visible. Ruska earned his Nobel Prize for this work, two years before his death, in 1986.

Discovery of the double helix

In 1944, Oswald Avery discovered that bacteria had nucleic acid. We know these nucleic acids as DNA and RNA. He also discovered that change in DNA affects structure of a bacteria. Structure of these nucleic acids was however unknown. In 1953, James Watson and Francis Crick used X-ray crystallography to reveal structure of DNA. This double-helix has since become a symbol of science. They shared 1962 Nobel Prize for this discovery.

Beyond the double helix

Today we know that our genes are a sequence of amino-acids. Amino-acids arranged in a double-helix form DNA. Further, DNA is coils over histone-proteins to form a chromosome. Human cells have 23 pairs of chromosomes. Mendel had correctly identified, that some “factors” or “genes” are dominant.

DNA is a dynamic structure. It is in a constant state of repair and disrepair. Enzymes such as telomerase and phosphorylase help to keep it together. Information from DNA is translated to a single-helix RNA. These RNAs and tiny ribosomes generate all our proteins and enzymes. These cellular processes and structures, have all earned a Nobel Prize for their discoverers.

In the last three decades we have discovered more governing molecules and structures. Crystallography has helped us identify many structures. Advances in molecular biology, on the other hand have helped us know our genes better. In 1990, scientists from across the world embarked on a “Human genome project.” We were able to sequence the entire length of human genome in 2003. This sequence is about 6 billion base pair long. This is a major landmark in our understanding of our governing molecules.

Some more biological advances in Postage stamps

We have come a long way in last 150 years. Gregor Mendel could only imagine governing traits. We have not only characterised them, but are well poised to exploit them for human health. Newer medicines are designed to bind with and inactivate molecules with undesirable actions. Hope we will have more of them in postage stamps.