What Is The Triplet Code? - YouTube
RNA molecule codes for a specific amino acid in protein synthesis
shows the genetic code of the messenger ribonucleic acid (mRNA), i.e. it shows all 64 possible combinations of codons composed of three nucleotide bases (tri-nucleotide units) that specify amino acids during protein assembling.
Each codon of the deoxyribonucleic acid (DNA) codes for or specifies a single amino acid and each nucleotide unit consists of a phosphate, deoxyribose sugar and one of the 4 nitrogenous nucleotide bases, adenine (A), guanine (G), cytosine (C) and thymine (T). The bases are paired and joined together by hydrogen bonds in the double helix of the DNA. mRNA corresponds to DNA (i.e. the sequence of nucleotides is the same in both chains) except that in RNA, thymine (T) is replaced by uracil (U), and the deoxyribose is substituted by ribose.
The process of translation of genetic information into the assembling of a protein requires first mRNA, which is read 5' to 3' (exactly as DNA), and then transfer ribonucleic acid (tRNA), which is read 3' to 5'. tRNA is the taxi that translates the information on the ribosome into an amino acid chain or polypeptide.
For mRNA there are 43 = 64 different nucleotide combinations possible with a triplet codon of three nucleotides. All 64 possible combinations are shown in . However, not all 64 codons of the genetic code specify a single amino acid during translation. The reason is that in humans only 20 amino acids (except selenocysteine) are involved in translation. Therefore, one amino acid can be encoded by more than one mRNA codon-triplet. Arginine and leucine are encoded by 6 triplets, isoleucine by 3, methionine and tryptophan by 1, and all other amino acids by 4 or 2 codons. The redundant codons are typically different at the 3rd base. shows the inverse codon assignment, i.e. which codon specifies which of the 20 standard amino acids involved in translation.
A nucleotide triplet code for amino acids - ScienceDirect
Har Gobind Khorana, at the University of Wisconsin, adapted Nirenberg's experimental system, and confirmed and extended his work. Nirenberg and Khorana were awarded the 1968 Nobel Prize in Physiology or Medicine, shared with Robert W. Holley, "for their interpretation of the genetic code and its function in protein synthesis."