The degenerate, universal genetic code determines that each amino acid is dictated by a set of three nucleotides, proving it is impossible to code for amino acids with overlapping triplets
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Brenner S. (1957). ON THE IMPOSSIBILITY OF ALL OVERLAPPING TRIPLET CODES IN INFORMATION TRANSFER FROM NUCLEIC ACID TO PROTEINS. Proceedings of the National Academy of Sciences of the United States of America, 43(8), 687–694. link
Slide 1: Researcher’s Background
Brenner is a biologist who worked with Dr. Francis Crick on the development of the “central dogma” of biology and was awarded a Nobel Prize for his genetic work with C.elegans, the first animal with its complete genome sequenced. He also played a key role in the discovery of mRNA and of STOP codon sequence during protein translation.
Biography in brief
Dr. Sydney Brenner was born in South Africa to Jewish parents. He never learned how to read and write but knew how to converse in five languages. He attended the the University of the Witwatersrand at the age of 15 studying medicine. He did his postdoctoral research at the University of California, Berkeley and spent the rest of his life working in molecular biology laboratories across the world making several contributions to this field. For example, he was the first to prove that the genetic code was non overlapping and he worked with Francis Crick on the development of the “central dogma” of biology. He received countless prizes and honours throughout his career for his discoveries.
Is (or was) their research under-valued because of their identity?
Are there other scientists/research examples that this example can replace or be added to?
James Watson and Francis Crick as he helped propose the concept of tRNA adaptor molecules and worked on the structure of DNA. He also shared the 2002 Nobel Prize in Physiology or Medicine with H. Robert Horvitz and John Sulston.
Slide 2: Research Overview
Take home message of study
The take-home message of this research is that the genetic code is non overlapping as each amino acid is interacting with at least two, if not three nucleotides. The general theorem that this research follows is the triplet code, where the four RNA nucleotides (A, U, G and C) are combined into 64 different triplets to code for different amino acids. Each amino acid can be represented by more than one triplet, thus the 64 different triplets only code for 20 different amino acids. This research has proven that the amino acid sequence cannot be overlapping because multiple triplets in a row share two nucleotides in common, and so they can only be preceded (N-neighbours) or succeeded (C-neighbours) by four different triplets. The table in the following question accounts for all combinations of amino acids, their C-neighbours and N-neighbours.
Using a correlational study design, Sydney Brenner studied the genome of the fugu fish, also known as the pufferfish, at the Institute of Molecular and Cell Biology (IMCB) in Singapore, in order to prove the triplet nature of the genome code and its non overlapping behaviour.
Slide 3: Key Research Points
This table proves that it is impossible to code amino acids with overlapping triplets, since the table above shows that 64 triplets are insufficient to code for the known sequences. The N and C neighbours in the table above are each one of the triplets assigned to the codon. Since successive triplets share two common nucleotides then for any triplet, it can only be preceded and succeeded by only four different triplets. Therefore, the minimum number of triplets for each amino acid can be deduced from the table of neighbours.
Dr. Brenner had many important discoveries in Molecular Biology but he specifically proved that the genetic code is non-overlapping, which means that the adjacent codons do not overlap. This is one of the essential characteristics of the universal genetic code used to identify the correct reading frame and translate amino acids into functional proteins. This code is shared by diverse organisms which provides evidence of the origin of life on Earth. His discovery was done through analysis and statistical methods without the use of technology, which is an amazing accomplishment and essential for Molecular Biology! Knowing and understanding how our DNA is structured will furthermore allow us to better understand our genes and how they may affect us. Such discovery allowed researchers to link specific diseases to specific genes.