Genetic Code

Introduction

The DNA genetic code is part of the original history of life. The RNA world hypothesis states that one version of self-reflecting RNA molecules is the sequence that preceded life. Living cells translate information interlaced with genetic material like codons and DNA & RNA sequences using a set of rules into protein. This set of rules is called the Genetic code. Ribosomes help accomplish the translation; ribosomes are the molecular kind of device found within cells. 

Ribosome and its Units

The function of ribosomes is to connect amino acids to the messenger RNA or mRNA molecule, in a particular order specified by the codons that will form a polypeptide chain. The two primary units of the ribosome are the large and small ribosomal subunits. In the upcoming protein synthesis, codons specify the particular amino acid that should be added. In a sequence of nucleic acid, only one single specified amino acid is required in the three-nucleotide codon, which can happen due to exceptions. 

In 1961, Heinrich J. Matthaei, Marshall, and Nirenberg initially revealed the nature of codons. They discovered the polypeptide they had synthesised using the cell-free method to translate the poly-uracil based RNA sequence. 

Genetic Code Definition 

The particular sequence of DNA nucleotides or codons decides the amino acid sequence in protein synthesis, which can be defined as the Genetic code. With the help of codons, genetic codes are understood in triplets of bases; in simpler words, a set of three nucleotides form a codon. The RNA sequence is based on a single amino acid in the triplet code. To produce signals of initiation or termination of the translation, there are 20 amino acids present to have corresponded with 64 codons. The code explains the mechanism that helps the genetic information stored in the living organism. 

Genetic Code Classification

Classified genetic codes are of two types: DNA codons and RNA codons. The occurrence of RNA codons happens in the mRNA or messenger RNA and are the specific codons in which translation takes place during the polypeptide synthesis. With the help of transcription from the corresponding gene, each messenger RNA takes a nucleotide sequence. Now genes are discovered at the DNA sequence level, but earlier, genes were discovered at the messenger RNA sequence level or as the protein product. 

The genetic information for the protein sequence is contained in the DNA in the form of the linear sequence of nucleotides, so the DNA sequence doesn’t directly make the protein. The four nucleotides components of the RNA sequence are Adenine(A), Guanine(G), Uracil(U), and Cytosine(C), where the four nucleotide components of the DNA sequence are Adenine(A), Guanine (G), Cytosine(C) and thymine(T). Every genetic code is formed from these four chemical nucleotides in different and various ways that spell out the three-letter word, which further specifies the particular amino acid required to make protein. 

Degeneracy of Genetic Code

The redundancy of genetic code is called degeneration, and Bernfield and Nirenberg termed it. The genetic code is degenerate because only a single amino acid might be coded for by more than one codon. It is essential to remember that the genetic code does not overlap, which means that the nucleotide is part of only one codon and cannot be part of two or more adjacent codons. Genetic code DNA is fairly universal; only a few variations are reported like mitochondria only has a slight alternative genetic code. Different genetic codes of various organisms can be inferred by simply recognising highly conserved genes encoded with the genome. A comparison is made between homologous proteins of other different organisms and their usage of codon to the amino acid. 

Conclusion

The particular sequence of DNA nucleotides or codons decides the sequence of the amino acid in protein synthesis, which can be defined as the Genetic code. With the help of codons, genetic codes are understood in triplets of bases; in simpler words, a set of three nucleotides form a codon. The genetic code DNA is part of the original history of life. Classified genetic codes are of two types: DNA codons and RNA codons. The genetic information for the protein sequence is contained in the DNA in the form of the linear sequence of nucleotides, so the DNA sequence doesn’t make the protein directly. The redundancy of genetic code is called degeneration, and Bernfield and Nirenberg termed it. The genetic code has degenerated because only a single amino acid might be coded for by more than one codon.