A codon is a set of three nitrogenous bases in a sequence of messenger RNA (mRNA) or DNA that encodes a specific amino acid in protein synthesis. Codons are fundamental elements in the process of genetic translation, where the sequence of codons in mRNA is read to determine the order in which amino acids are assembled to form proteins.
Characteristics of codons
Each codon is made up of three nucleotides, the subunits that make up nucleic acids. These nucleotides are grouped into triplets in a specific sequence that is recognized by ribosomes during protein synthesis. The nitrogenous bases that make up a codon can be adenine (A), cytosine (C), guanine (G) and uracil (U) in mRNA or thymine (T) in DNA.
In DNA , the codon sequence is transcribed into mRNA during the transcription process. This mRNA sequence is then read by ribosomes in the cell cytoplasm during translation to assemble the correct amino acid chain according to the genetic information stored in the genes.
Universal and redundant
Codons are universal, meaning that most organisms use the same genetic code to translate genetic information into proteins. Although there are some variations in the genetic code of certain species, in general, the codons are read the same in most living things.
In addition, the genetic code is redundant, meaning that Most amino acids are encoded by more than one codon. For example, there are up to six different codons that code for the amino acid leucine. This redundancy allows for greater robustness in genetic transcription and translation, since an error in the reading of a single codon will not always result in the incorporation of an incorrect amino acid into the final protein.
Codon functions
Amino acid coding
The main function of codons is to encode genetic information that determines the order in which amino acids are assembled during protein synthesis. Each codon specifies a particular amino acid, with the exception of the start and stop codons that mark the start and end of translation.
During the translation of mRNA into proteins, ribosomes recognize the start codons. (AUG in most cases) and begin reading the codon sequence to add the corresponding amino acids. As the ribosomes advance along the mRNA, they join the amino acids in the specific sequence indicated by the codons.
Initiation and completion of translation
In addition to their function in Coding for amino acids, codons also include start and stop signals for protein translation. The start codon (AUG) tells the ribosome where to start protein synthesis, while the stop codons (UAA, UAG, UGA) mark the end of the polypeptide chain and stop translation.
Regulation of gene expression
Codons not only code for amino acids, but also play a role in regulating gene expression. Some codons act as pause signals to slow or stop translation, allowing error correction or protein modification in process to take place.
In addition, certain codons can have regulatory effects on translation. translation speed or stability of mRNAs. For example, the presence of rare or slow codons can influence the efficiency of translation and, therefore, the amount of protein produced from a specific gene.
Conclusions
In summary, codons are sequences of three nucleotides that code for specific amino acids during protein synthesis. Its universal and redundant structure provides a robust system for genetic translation in most living organisms, allowing precise synthesis of proteins from the genetic information stored in genes. In addition to their role in coding amino acids, codons also play roles in regulating gene expression and signaling the initiation and termination of protein translation.