Genetic code - A set of three nucleotides

 

• The  genetic representation of codon by which the information in mRNA  is transformed in a polypeptide chain is called genetic code.

• Genetic code is also defined as genetic code is the relationship of amino acid sequences in a polypeptide chain and base sequence of DNA. 

• George Gamow argued that  there are only four bases on RNA  and if they have to code for twenty amino acids the code should constitute a combination Of three bases.

• In order to code for all 20 amino acids the code should be made up of three nucleotides. And there are only 64 genetic codes that all are required to code all 20 amino acids by a hypothesis. This hypothesis is known as the wobble hypothesis. This hypothesis was given by FHC CRICK. 

Read about the Protein Synthesis 

• According to this third nitrogenous base of a codon wind loosely with the anticodon and codon is mainly specified by first two bases has the same tRNA can recognise more than one codon differ at third position. 

• The chemical method for the synthesising RNA molecule with a defined combination of bases was done by an Indian scientist Dr Hargovind Khurana.

• Severo ochoa enzyme was also helpful in polymerisation of RNA  with defined  sequence. 

👌👌Remember First genetic code was discovered by Nirenberg  and Matthaei. The genetic code  that was discovered by them was UUU.

• Holley, Nirenberg, and Khorana were awarded the Nobel Prize in 1968 for deciphering the genetic code. 

• The silent feature of genetic code are as follow-

• The genetic code is universal. It means it is found in all living organisms from bacteria to humans. 

• A genetic code code for an amino acid in all organisms from bacteria to human beings.

Read about the bacteria

• For example UUU would code  the amino acid phenylalanine from bacteria to human beings. 

• For a particular amino acid more than one codon can be used. This is called the genetic code is degenerate. 

• Genetic codes are non overlapping. That means the same letter cannot be used for two different codons. 

• A particular codon will always code for same amino acid that means the genetic code non  ambiguous but AUG  when present in beginning code for Methionine  but when present in the intermediate position  it code for Valine. 

• The Genetic   code which initiates the protein synthesis called initiation codon. The initiation codon is AUG. It also Code Methionine  amino acid.

• The codon which cannot code  any amino acid is called nonsense codon or Terminator codon. There are three terminator codons. These are UAG UAA UGA.