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Researchers from the University of Cambridge have created the first living organism with a genome that's been completely redesigned in the lab. This feat is another step forward in understanding how genetics works in the minutest of details.
The team recorded the genome of a strain of Escherichia coli and, as reported in Nature, were able to deliver a synthetic version of the bacterium, which, despite some differences, is healthy and able to reproduce. The team showed that the edited version, known as Syn61, can produce the same quantity and types of proteins as the original E. coli. The main differences are in Syn61's length and reproduction. The microbes are a bit longer than normal and take 60 percent more time to reproduce.
The genetic code of every (known) living organism is written in a very specific language. The letters of DNA are given by the nucleic bases: adenine, thymine, cytosine, and guanine or A, T, C, and G. These are organized into 64 triplets known as codons. Sixty-one codons correspond to amino acids, the building blocks of proteins. The other three act as “stop” signals that are recognized by the protein-manufacturing organelles inside cells.
Now, there are only 20 amino acids used in nature, so some codons are synonymous and correspond to the same amino acid. But just as a piece of text can be ruined by a weird synonym, switching one codon for another can be detrimental to the whole genetic code.
Scientists were intrigued by the possibility of being able to understand which codons are crucial and which can't be switched. They looked into a codon compression technique that would restructure the bacterium's genome with fewer possible codons. To give a nerdy simile, just think of how the hobbits in The Lord of the Rings are referred to as both "hobbits" and "halflings". If this was changed so that they were only ever called hobbits, the language might be different, but the overall story would remain intact.
The researchers were able to go through the 4 million bases of the E. coli genome and recode 18,214 codons. They managed to entirely remove three codons from the whole genome. Syn61 uses only 61 codons instead of 64 for protein synthesis. It has lost two codons that encode the amino acid serine and one of the three stop codons.
"It was completely unclear whether it was possible to make a genome this large and whether it was possible to change it so much," biologist Jason Chin told The Guardian.
This is not the first lifeform with a synthetic genome, but it is the first one to have changes made on such a scale.
[H/T: The Guardian]
