Most of us have a playlist of our favourite songs we listen to in an order or sequence.
Similarly, even DNA has nucleotides (nucleoside+phosphate group) arranged in an order. The process of determining this order is nothing but DNA sequencing. DNA is called the Blueprint of life as it contains the instructions needed for an organism to grow, develop, survive and reproduce.
Like each of us has a different playlist and order of songs, each organism's DNA differs in the order in which the nitrogen-based molecules are arranged. The sequence of DNA reveals a lot of genetic information, which helps identify genes and mutations that can cause diseases. The DNA sequence also confers information that the cell uses to make RNA molecules and proteins; establishing the sequence of DNA is key for understanding how genomes work.
The events in our lives happen in a sequence in time, but in their significance, to ourselves, they find their order, the continuous thread of revelation- by Eudora Welty
One such revelation was DNA sequencing by Frederick Sanger and his colleagues. Federick Sanger was an English biochemist who won the Nobel Prize in Chemistry twice.
He first explored the possibility of sequencing RNA and then moved to sequence DNA.
As you know, ‘Success is best when it's shared. So after a lot of research and trials in 1977, Sanger and his colleagues presented the 'Dideoxy' Chain termination method, also known as the Sanger method for sequencing DNA molecules. It involves electrophoresis and random incorporation of chain-terminating dideoxynucleotides by DNA polymerase. This was a major breakthrough at that time as long stretches of DNA could be sequenced faster with more accuracy.
In 1977, Sanger used his method to sequence the first ever complete genome: the bacteriophage PhiX174 (a virus that infects E. coli) which had around 48,502 base pairs. In 1981, also he used this method to sequence the human mitochondrial DNA which had around 16,569 base pairs
Did you know?
The human genome, our total DNA, was first entirely sequenced in 2003. The effort took 13 years and cost three billion U.S. dollars.
Over the years, many new and advanced methods have been developed for DNA sequencing, but Sanger sequencing is still used in small-scale projects to validate profound sequencing results. It is also majorly used for sequencing individual pieces or DNA fragments for DNA cloning and in Polymerase Chain Reaction(PCR). The human genome can now be sequenced for $1000 in less than two weeks.
During the Pandemic, the Sanger sequencing method was used for sequencing the spike protein from SARS-CoV-2( Severe acute respiratory syndrome coronavirus 2), a strain of coronavirus that causes COVID-19.
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