How big and complex is our genetic code

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Our body is a collection of cells, that give shape to our organs, structure, function, thoughts, language, and behaviour. We are a collection of about 30 trillion cells and 38 trillion bacteria who live within. Each of these cells have a beginning. It was a single cell when our lives began, and then over a few months they became many. Each cell has its destiny. Genetic material or DNA in each cell, is responsible for this destiny.

On 25th April 1953, James Watson, Francis Crick, Maurice Wilkins, Rosalind Franklin and colleagues published broad structure of our DNA. This double helix carries our genetic code. This code is a sequence of nucleic acids, arranged in a neat pair, and is tightly packed in our chromosomes. This discovery was just a beginning.

The complexity of our DNA

All precursor human cells have 23 pairs of chromosomes. These chromosomes is like a DNA packaging. Here double helix is tightly wrapped around some proteins. Overall there are 3 billion base-pairs of DNA in each of these cells. Only some parts of this DNA are active in every cell. This activity or expression decides, what will a cell become. For instance, some cells shape our heart and vessels, and others our brain and nerves. Some scientists had a desire to know the entire sequence, or code as we call it.

Parts of DNA help produce a variety of proteins in our body, and these proteins (such as enzymes, receptors, or cytokines) determine behaviour of each of these cells. Our key interest was in these ‘active’ parts of DNA. Other sections of DNA that were ‘not-so-active’. Over the years we have realised that both these parts are important. The ‘not-so-active’ ones actually control the ‘actives’. Isn’t it quite similar to human societies.

First breakthrough in our understanding of the code, was our ability to extract DNA from the cells. Then we learned the process of breaking it in shorter fragments. Over the years we had the code for some of these short pieces. So by early 1980s, we had a sense of our code, but in bits and pieces.

Our Genes are nothing but a DNA sequence

In 1984, Renato Dulbecco argued that knowing the human genome sequence would actually be helpful. This knowledge, he argued would solve mysteries behind cancers. Many others were sceptic. Such a task was complex, expensive, and its benefits uncertain. Eventually by 1988, the idea found political and then financial support. Thus, in 1990 many scientists from across the world embarked on a “Human Genome Project“. Its aim was to know it all, the entire 3 billion base pair sequence. This remains the largest collaboration for a biological project, till date.

To list, count and confirm each of the 3 billion base pairs of our genome was not easy. Two processes of improvement in technology and deciphering of the code were running in parallel. As a part of the project, we also sequenced some smaller organisms, such as some bacteria, yeast, fruit-flies, some plants and even mice . Overall about 20 centres across the world were part of this collaboration. A key aspect of the project was agreement on data-sharing. This agreement was that the parts of code, will not be a secret, and shall be published with 24hrs of its unraveling. This was a first such process, that really accelerated the project.

Completion of Human Genome Project

In 2001, scientists had figured out a rough draft of 90% of human genome. So in the beginning of the year 2003, we knew that final pieces of the puzzle were just around. In February 2003, Britain issued a set of five postage stamps

And this five-stamp set cover and cancellation issued on 25th February sums up it all. “Our fate is in our genes” and “DNA is the secret of Life.”

Scientists announced completion of human genome project on 14th April 2003. This was when 96% of all genetic material was known. The remaining 4% were small non-coding sequences. This 2003 success was a mere 50 years after we first knew DNA as a double helix.

So, how big and complex is our code

Our entire genetic sequence turned out to be much more complex than what we initially thought. To our surprise, about 40% of human genome is similar to a fruit-fly. Most of the code is similar in any two unrelated humans. Further, some chromosomes have more ‘active’ or protein-coding parts, as compared to others. Only 2% of the entire sequence codes for proteins, which is less than 20,000 genes in all.

Unfortunately, even 20 years after 2003 sequencing, we still donot know ‘the secret of life’. The sequence raised more questions than answers. If genetic material across species is mostly similar, what makes each of us different. Probably the answer lies in what is expressed. We still do-not know how. After 2003, we began the process of analysing the code. This project ENCODE (Encyclopedia of DNA Elements) is our attempt to understand how does our code function. This is still a work in progress.

Hopefully, one day, we will know secret of our lives !!