We explain what the genetic code is, its function, composition, origin and other characteristics. Also, how was its discovery.
What is the genetic code?
The genetic code It is the specific arrangement of the nucleotides in the sequence that makes up DNA . It is also the set of rules from which said sequence is translated by RNA into a sequence of amino acids, to compose a protein. That is to say that Protein synthesis depends on this code .
All living beings have a genetic code that organizes your DNA and RNA. Despite the obvious differences between the different kingdoms of life, the genetic content turns out to be largely similar, suggesting that all life must have had a common origin. Tiny variations in the genetic code can give rise to a different species .
The genetic code sequence comprises combinations of three nucleotides each called a codon and responsible for synthesizing a specific amino acid (polypeptide).
These nucleotides come from four different types of nitrogenous bases: adenine (A), thymine (T), guanine (G) and cytosine (C) in DNA, and adenine (A), uracil (U), guanine (G) and cytosine (C) in RNA.
In this way a chain of up to 64 codons is built 61 of which make up the code itself (i.e., synthesize amino acids) and 3 mark start and stop positions in the sequence.
Following the order that this genetic structure determines, the body's cells can gather amino acids and synthesize specific proteins, which will fulfill specific functions in the body.
Features of the genetic code
The genetic code has a series of basic characteristics, which are:
- Universality As we have said before, all living organisms share the genetic code, from viruses and bacteria to people, plants and animals. This means that a specific codon is associated with the same amino acid, regardless of which organism it is. There are 22 different genetic codes known, which are variants of the standard genetic code in just one or two codons.
- Specificity The code is extremely specific, that is, no codon codes for more than one amino acid, without overlapping occurring, although in some cases there may be different start codons, which allow different proteins to be synthesized from the same code.
- Continuity The code is continuous and has no interruptions of any kind, being a long chain of codons that is always transcribed in the same sense and direction, from the start to the stop codon.
- Degeneration The genetic code has redundancies, but never ambiguities, that is, two codons can correspond to the same amino acid, but never the same codon to two different amino acids. Thus, there are more different codons than is minimally necessary to store genetic information.
Discovery of the genetic code
The genetic code It was discovered in the 1960s after the Anglo-Saxon scientists Rosalind Franklin (1920-1958), Francis Crick (1916-2004), James Watson (1928) and Maurice Wilkins (1916-2004) discovered the structure of DNA, beginning the genetic study of synthesis protein cell.
In 1955, scientists Severo Ochoa and Marianne Grunberg-Manago managed to isolate the enzyme polynucleotide phosphorase. They found that in the presence of any type of nucleotides, this protein built an mRNA or messenger composed of the same nitrogenous base, that is, a polypeptide of a single nucleotide. This shed light on the possible origin of both DNA and RNA.
The Russian-American George Gamow (1904-1968) proposed the genetic code model formed by combinations of the nitrogenous bases known today. However, Crick, Brenner and their collaborators demonstrated that codons are made up of only three nitrogenous bases .
The first evidence of correspondence between the same codon and an amino acid was obtained in 1961 thanks to Marshall Warren Nirenberg and Heinrich Matthaei.
Applying their methods, Nirenberg and Philip Leder were able to translate 54 of the remaining codons. Subsequently, Har Gobind Khorana completed the transcription of the code. Many of those involved in this race to decipher the genetic code were winners of the Nobel Prize in Medicine.
Function of the genetic code
The function of the genetic code is vital in the synthesis of proteins, that is, in the manufacture of the basic elemental compounds for the existence of life as we understand it. That's why, It is the fundamental pattern for the physiological construction of organisms both its tissues and its enzymes, substances and fluids.
To do this, the genetic code operates as a template in DNA, from which RNA is synthesized, which is a kind of mirror image. Then, RNA moves to the cellular organelles in charge of building proteins (ribosomes).
In the ribosomes, synthesis begins according to the pattern that passed from DNA to RNA . Each gene is thus associated with an amino acid, building a polypeptide chain. This is how the genetic code works.
Origin of the genetic code
The origin of the genetic code is probably life's greatest mystery. It is intuited, given that it is common to all known living beings, that Its appearance on the planet was prior to that of the first living being that is, the primitive cell that would give rise to all the kingdoms of life.
Initially, It is likely that it was much less extensive and had only the information to encode a few amino acids, but would have grown in complexity as life emerged and evolved.
References
- “Genetic code” in Wikipedia.
- “Genetic code – biotechnology” (video) in Educatina.
- “The genetic code” in Khan Academy.
- “Genetic code” at National Human Genome Research Institute.
- “The genetic code” in BioInnova.
- “Genetic code” in The Encyclopaedia Britannica.
