Scientists have finally done what was once considered improbable, but never impossible decoding the entire human genome.
Researchers have filled the gaps, completing an end-to-end sequence of the roughly 3 billion bases (or “letters”) in our DNA (deoxyribonucleic acid), which is critical to understanding human genetic diversity. The development has the potential of unlocking ways to enhance human health.
Since its initial release in 2000, the human reference genome did not cover the entire sequence leaving important heterochromatic regions unfinished, said the researchers whose study was published in the journal Science. About 92 per cent of the genome was fully known.
Addressing the remaining 8 per cent of the genome, the Telomere-to-Telomere (T2T) Consortium has now presented a complete 3.055 billionbase pair sequence.
WHAT IS THE HUMAN GENOME?
A genome is a chemical compound. It represents an organism’s complete set of DNA. It contains all the information of the past evolution and codes for instructions needed to develop and direct activities to run the life of the organism.
A set of DNA is made of two twisting paired strands, often referred to as a double helix. A unit of DNA containing particular set of attributes and information is called gene the word more commonly used by people to refer to hereditary matters.
According to the National Human Genome Research Institute, each DNA strand is made of four chemical substances, called nucleotide bases. These bases carry what we call the genetic information. Each base is represented by one of the four letters A, T, C and G. They are arranged in pairs.
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.
DECODING HUMAN GENOME
The full sequencing builds on the work of the Human Genome Project, which mapped about 92% of the genome. Researchers said that the last eight per cent includes numerous genes and repetitive DNA and is comparable in size to an entire chromosome.
They generated the complete genome sequence using a human cell line with only one copy of each chromosome, unlike most human cells, which carry two copies of each chromosome.
Each strand of the human DNA is made up of a pair of chromosomes, drawing one each from the parents.
The Telomere to Telomere (T2T) consortium’s full version is composed of 3.055 billion base pairs the units from which chromosomes and our genes are built and 19,969 genes that encode proteins.
Of these genes, the researchers identified about 2,000 new ones. Researchers also spotted about 2 million additional genetic variants, 622 of which were present in medically relevant genes.
“Ever since we had the first draft human genome sequence, determining the exact sequence of complex genomic regions has been challenging. I am thrilled that we got the job done.”
“The complete blueprint is going to revolutionize the way we think about human genomic variation, disease, and evolution,” Evan Eichler, a researcher at the University of Washington and T2T consortium co-chair said.
OVER TWO DECADES OF WORK
The work on decoding the human genome came to light more than 20 years ago. Researchers released the first set of the human genome sequence in 2001. However, it was just 85 per cent complete and 15 per cent remained hidden away. This 15 per cent turned out to be the most complex set of variations that have eluded scientists the world over for decades.
The researchers came a step closer to the monumental discovery in July last year when a 99-member team of the consortium made the groundbreaking discovery by identifying about 115 new genes that code for proteins.
The finding provided new insights into the workings of the DNA how it influences the risks of disease and how cells keep it neatly organised.
WHY IS DECODING THE HUMAN GENOME SO CRITICAL?
Decoding the human genome opens up new avenues of research to enhance human health and find new ways to treat diseases and identify genetic diversities behind them.
With the full genome sequence now available, researchers can create a more accurate map of chromosomes, and thus, of the DNA. They can find answers to basic biological questions about how chromosomes properly segregate and divide.
It will be particularly valuable for studies that aim to establish comprehensive views of human genomic variation, or how people’s DNAs differ. Such insights are vital for understanding the genetic contributions to certain diseases, and the DNA’s response during fighting a disease, including a new one. This can become a routine part of clinical care in the future.
“In the future, when someone has their genome sequenced, we will be able to identify all of the variants in their DNA and use that information to better guide their healthcare.”
“Truly finishing the human genome sequence was like putting on a new pair of glasses. Now that we can clearly see everything, we are one step closer to understanding what it all means,” consortium co-chair Adam Phillippy said.