What is genetic code and its features?

Introduction:

The process of creating a protein using the information in RNA is comparable to translating a language. During protein synthesis, a four-letter language is converted into a 20-letter language. The 20 amino acid sequence in the protein should have a specific relationship to the four DNA bases.

What is the genetic code?

The genetic code is the base triplet of DNA and RNA that carries the genetic information for protein synthesis, specifies the amino acids, and specifies the start and stop codons for replication in the ribosomes.

Example: AUG is the start codon that codes for methionine.

Why is the genetic code triplet code?

Francis Crick and his colleagues experimentally proved that the genetic code is a triplet code or consists of three letters. In its explanation, we can say that the genetic material consists of four nucleotides (A, T, G, C) in different arrangements in the DNA molecule. Again, during protein synthesis through these different arrangements, 20 types of amino acids are added in different ways to make polypeptides or proteins. now-

1. If one nucleotide of DNA formed an amino acid signal, then only 4 amino acids would form all meats/proteins. which is not realistic.

2. Again, if two nucleotides or nitrogen bases are used as signals for an amino acid, then a maximum of (4 × 4) = 16 combinations can be found. This is also not realistic.

3. But if an amino acid signal is formed by the combination of three bases then (4×4×4) = 64 possible signals are obtained which are enough for the attachment of 20 amino acids. So genetic code is triplet code.

What are sense codon, signal codon, and anticodon?

Sense codons: The codes that directly control the synthesis of amino acids are called sense codons. 61 sense codons exist for the synthesis of 20 amino acids out of 64 codons.

Signal codons: The codes that give instructions to start or stop the synthesis of amino acids and polypeptide chains during protein synthesis are called signal codons. Signal codons are of 2 types; Namely:

1. Start or Initial codon: The codon that signals the beginning of amino acid and polypeptide chain synthesis during protein synthesis is called the initiation codon. For E.g. AUG is an initiation codon that codes for methionine.

2. Stop or Termination codon: The codons which give instructions or signals to stop the synthesis of amino acids and polypeptide chains during protein synthesis are called termination codons. the termination codon 3; Namely: UAA, UAG, and UGA. They play no direct role in the synthesis of any amino acid, hence they are called non-sense codons.

Anticodon: During protein synthesis, the messenger mRNA carried by DNA produces codons containing its own three nitrogenous bases. It then moves out of the nucleus to the ribosome. At this time, the special arrangement that the bases of tRNA form with the mRNA bases is called anticodon to retrieve the message carried by the mRNA. Anticodons are usually  3′ to 5′ because codons are 5′ to 3′.

What are the properties of genetic code?

Various experiments have determined the properties of the genetic code. Below are the characteristics of the genetic code.

Triplet Code: The genetic code consists of three letters or triplet codes.

The genetic code is unambiguous: a code specifies only one amino acid.

The genetic code is universal: that is, a specific code carries the same meaning in all organisms.

The genetic code is intransitive: meaning that the letters of one code do not overlap with other codes.

The genetic code is comma-free or punctuated: that is, there are no extra nucleotides between the two codes.

Degenerating genetic code: i.e. more than one code can specify an amino acid.

The chain starts and stops respectively with start and termination codons: Start and termination codons are specific. The chain starts with AUG and the chain ends with UAA, UAG, or UGA.

Conclusion:

The secondary structure of DNA plays a significant role in a variety of cellular processes. Numerous genes' transcription, replication, and regulation of expression are influenced by regional variations or alterations in DNA structure. Recombination that results in gene rearrangement makes use of the capacity to create an unusual structure known as Holliday's structure. Additionally, as a result of a particular DNA structure, various types of mutations take place. The ability of proteins to recognize clearly defined regions of DNA is enabled by a variety of mechanisms, including activation and inhibition of the expression of numerous genes, methylation, and base-cleavages of DNA. One of these mechanisms is the recognition of regional differences in secondary structure.