genetic code



We explain what the genetic code is, its function, composition, origin and other characteristics. Also, how was its discovery.

RNA is responsible for using the DNA code to synthesize proteins.

What is the genetic code?

The genetic code is the specific ordering of nucleotides in the sequence that makes up the DNA. It is also the set of rules from which said sequence is translated by the RNA in an amino acid sequence, to compose a protein. In other words, protein synthesis depends on this code.

All the living beings They have a genetic code that organizes their DNA and RNA. Despite the obvious differences between the various kingdoms of life, the genetic content turns out to be similar to a large extent, suggesting that the entire life it must have had a common origin. Tiny variations in the genetic code can give rise to a different species.

The sequence of the genetic code 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 (that is, they synthesize amino acids) and 3 mark start and stop positions in the sequence.

Following the order that this genetic structure determines, the cells The body can gather amino acids and synthesize specific proteins, which will fulfill certain functions in the body.

Characteristics 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 virus Y bacteria until persons, plants Y animals. This means that a specific codon is associated with the same amino acid, no matter what 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 highly specific, that is, no codon codes for more than one amino acid, without overlapping, 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 codon 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 the Genetic information.

Discovery of the genetic code

Nirenberg and Matthaei found that each codon encoded an amino acid.

The genetic code was discovered in the 1960s, after Anglo-Saxon scientists Rosalind Franklin (1920-1958), Francis Crick (1916-2004), James Watson, and Maurice Wilkins (1916-2004) discovered the DNA structure, starting the genetic study of cellular protein synthesis.

In 1955 the 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 made up of the same nitrogen base, that is, a single nucleotide polypeptide. This shed light on the possible origin of both DNA and RNA.

The Russian-American George Gamow (1904-1968) proposed the model of the genetic code formed by combinations of the nitrogenous bases known today. However, Crick, Brenner and their collaborators showed 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 crack the genetic code were awarded the Nobel Prize in Medicine.

Function of the genetic code

In ribosomes, the codon sequence is translated into amino acid sequence.

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 the life as we understand it. Therefore, it is the fundamental pattern for the physiological construction of organisms, both of its tissues, and of its enzymes, substances and fluids.

For this, the genetic code operates as a template in DNA, from which RNA is synthesized, which is a kind of mirror image. Then in RNA it moves to the cellular organelles responsible for the construction of proteins (ribosomes).

In ribosomes, synthesis begins according to the pattern that passed from DNA to RNA. Each gene is thus associated with an amino acid, building a chain of polypeptides. This is how the genetic code works.

Origin of the genetic code

The origin of the genetic code is probably the greatest mystery in life. It is intuited, since 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 kingdoms of life.

Initially, it is likely that it was much less extensive and had just the information to code for a few amino acids, but it would have grown in complexity as life arose and evolved.

!-- GDPR -->