Scientists complete decoding human genome, uncover over 100 new genes, variations

Reference:
https://www.indiatoday.in/science/story/human-genome-sequencing-dna-life-science-medicine-1833605-2021-07-28

Scientists deciphered the complete human genome twenty years after the first draft was released in 2001. Now they have uncovered over 100 new genes.

In February 2001, when researchers released the first set of the human genome sequence, it was a seismic event in the history of life sciences. However, it was not truly complete and 15 per cent of the genome was still to be deciphered. The most complicated chunk of DNA called for further research and technological advancement.

Twenty years later, researchers have finally deciphered it all filling the gaps in the long list of errors in previous versions and changing our view of human DNA. A team of 99 researchers led the groundbreaking discovery by identifying about 115 new genes that code for proteins.

The Telomere-to-Telomere (T2T) Consortium, an international collaboration that comprises around 30 institutions, has released data that gives new insights into the workings of the DNA and how it influences risks of disease and how cells keep it in neatly organised. Experts say that the new details will open our eyes to critical information stored within DNA that had remained elusive forever.

What is the human genome?

A genome is an organism’s complete set of Deoxyribonucleic acid (DNA), the chemical compound that contains the instructions needed to develop and direct the activities of nearly all living organisms. They are made of two twisting, paired strands often referred to as a double helix. According to the National Human Genome Research Institute, each DNA strand is made of four chemical units, called nucleotide bases, which comprise the genetic “alphabet.”

Virtually every single cell in the body contains a complete copy of the approximately 3 billion DNA base pairs, or letters, that make up the human genome. With its four-letter language, DNA contains the information needed to build the entire human body.

Why it took so long to decipher human genome?

Scientists identified 3.055 billion base pairs (“letters”) of our DNA code as they made the data public. However, the wait has been over two decades since the first draft was released in 2001. Scientists have known for decades that genes were spread across 23 pairs of chromosomes. However, their structures have been a mystery. The work on unravelling these mysterious structures began by the end of the 20th century.

Researchers found that genes make a very small percentage of the genome, much of which is made up of virus-like stretches of DNA that make new copies of themselves. They broke the genome into very small fragments of about 200 base pairs, deciphering their sequences, and then piecing them back together.

However, when researchers began working on solving these structures, they found that the twin strands of DNA in our cells contained roughly three billion pairs of letters. Assembling the puzzle of DNA bits was more complex than they had expected, and it took years to assemble.

As long stretches of the genome remained unknown, scientists struggled to understand where millions of bases fit. While they released the first draft in 2001, the reference genome draft was released in 2013 where they had read these fragments more accurately.

Adam Phillippy, a computational biologist at the National Human Genome Research Institute, who was part of the Telomere-to-Telomere Consortium told The New York Times that “The incomplete sequences were just really bugging me. You take a beautiful landscape puzzle, pull out a hundred pieces, and look at it — that’s very bothersome to a perfectionist.”

What is the Human Genome Project?

The Human Genome Project that first realised its goal in 1988 aimed to decipher the human genome in three major ways:

  • Determining the order, or “sequence”, of all the bases in our genome’s DNA
  • Making maps that show the locations of genes for major sections of all our chromosomes
  • Producing what is called linkage maps, through which we inherit trait

The project has revealed that there are probably about 20,500 human genes and the information about their structure, organization and function can be “thought of as the basic set of inheritable ‘instructions’ for the development and function of a human being.”

A startling finding of this first draft was that the number of human genes appeared to be significantly fewer than previous estimates, which ranged from 50,000 genes to as many as 1,40,000.

“It’s a history book – a narrative of the journey of our species through time. It’s a shop manual, with an incredibly detailed blueprint for building every human cell. And it’s a transformative textbook of medicine, with insights that will give health care providers immense new powers to treat, prevent and cure disease,” Francis Collins, then director of the National Human Genome Research Institute had said in 2001.