The Genetic Code: History, Facts, and Resources

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The genetic code is a set of complex instructions that are coded into all genetic materials, including DNA and mRNA. These detailed instructions tell the cells how they should grow and develop. On a more technical level, genetic code is the chemical language that translates the language of nucleic acids into the language of amino acids.

RNA and DNA Resources

A Molecular Graphics companion to an Introductory Course in Biology or Biochemistry. Copyright 1995, Richard B. Hallick.
Recombinant DNA (rDNA): Technology, Plasmids, and Resources
Computer Model of the DNA Helix
DNA Structure: DNA is usually a double-helix and has two strands running in opposite directions.
RNA Structure: Ribonucleic Acid (RNA): Facts, Information About Its Role in Protein Synthesis, and Resources.
albany.edu RNA Modification Database

The instructions, often referred to as mapping, tell the cell exactly how it should react in any given case. For example, if the cell encounters the sequence adenine, adenine, the amino acid lysine should be produced. The code, which is followed in repetition, will continue to perform over and over, creating amino acids that form proteins.

The genetic code has certain distinctive features, such as that there are triplets called codons, with each amino acid specified by a codon consisting of three bases. And each position of the codon can have any one of the four purine or pyrimidine bases. In other words, there are 64 triplets (codons) of nucleotides.

Most genes are encoded with the same code, which is referred to as the standard genetic code. All organisms, whether the simplest bacteria or a complex human being, use the same genetic code. There are, however, some exceptions to the universal genetic code. Most of these very rare exceptions are found in in the mitochondrial genome ( a combination of the words gene and chromosome).

The genetic code was discovered by Francis Crick between 1953 and 1966. He is responsible for deciphering the code that distinguish the difference between living organisms from non-living things. On a basic level, he answered the question, “What is life?” Crick did not perform this work alone however, and others including James Watson, Maurice Wilkins, Har Gobind Khorana, and Rosalind Franklin also contributed to the discovery of the genetic code.

While Crick and his esteemed colleagues were responsible for cataloging the genetic code, they did not necessary explain how it originated. There are two main thoughts around the explanation of the origin of the genetic code: Crick’s frozen accident and Woese’s amino acid-codon specific chemical interaction.

Woese’s theory states that the code is universal for stereochemical reasons, while Crick’s theory states that the genetic code is universal because changing anything in the code would be damaging or deadly. Both theories continue to be debated among scientists today.

A study was done to analyze tRNA sequence relatedness to determine the age of the genetic code. The researchers in the study concluded that while the genetic code is not older than Earth itself, it is nearly as old. Their theory was that the origin of genetic code and the structure of tRNA existed in primal cells. They believe there is evidence that has been left behind to demonstrate a secondary structure in tRNA. The great uniformity in the genetic code also have some scientists arguing that the genetic code is perhaps older than life itself.

In previous years, the general assumption was that genetic code remained static, but in more recent years of research, beginning with the work by Barrel, Bankier and Drouin in 1979, it is suggested that the genetic code is actually in a constant state of evolution. By understanding how the current genetic code evolved, scientists hope to understand how the code will continue to alter itself.

While there are differences of opinions within the scientific community about the nature of the genetic code, there are some conclusions that are almost universally accepted. That is, nearly all living things use the same, genetic code, and that the genetic code seems to be about the same age as the Earth.

Genetics Resources

Learn Genetics from utah.edu
University of Chicago’s: The Department of Human Genetics is the home within the Division of Biological Sciences for the study of basic principles of genetics and genomics as applied to human disease.
Kumc.edu’sGenetics Education Center

Resource by AnnaBelle

Annalise Kaylor is a freelance writer, editor, and consultant specializing in search engine optimized content for the web. As a writer, her work has appeared across the United States in print ads for Whirlpool, Maytag, Home Depot, and Lowe's, among others. As a consultant, she has worked primarily in the education sector, helping universities increase their web visibility and construct and implement social media strategy. Annalise is an avid reader, knitter, organic gardener and baker, as well as the author of the popular baking blog, Knead To Be Loaved. Annalise enjoys fly fishing, camping, and hiking.

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