DNA is the genetic material of most organisms. A DNA molecule is made up of a series of nucleotides. This nucleotide series represents the whole genetic information of the organism. The protein coding regions within the nucleotide series are known as genes. The information of a particular protein is coded by nucleotide triplets within the gene known as codons. Each nucleotide triplet represents a specific amino acid of the polypeptide chain. The whole set of codons is known as the genetic code, and it is used to code the information of a protein within a gene.
Key Areas Covered
Key Terms: Amino Acid, Codon, Genetic Code, Protein, Transcription, Translation
What is Genetic Code
The genetic code refers to the set of rules by which the genetic information is encoded within the genetic material. It defines how the four-letter code of DNA is translated into the twenty-letter code of amino acids. The amino acids are the building blocks of the proteins. Each amino acid is represented by a code of three nucleotides known as a codon. The genetic code that represents the 20 amino acids is shown in figure 1.
64 codons are included in the genetic code, and 61 codons among them represent amino acids; the rest are stop codons. One of the characteristic features of the genetic code is its degeneracy. This means a single amino acid can be represented by more than one codon. Some other features of genetic code are:
- genetic code does not overlap
- a single nucleotide cannot be a part of two adjacent codons
- the genetic code is nearly universal.
How Does DNA Code for Proteins in a Cell
Genes are elements of the genome that code for proteins. Genes are made up of a series of nucleotides. This nucleotide series represents a series of codons. Each codon represents a particular amino acid in the polypeptide chain. This codon series is transcribed into a mRNA during transcription and is decoded into an amino acid sequence of a functional protein during translation. The production of a protein by the use of genetic information in a gene is shown in figure 2.
The genetic information for proteins is encoded by the genes in the genome. The genes are made up of a series of nucleotides. These nucleotides are grouped into three resultant codons. Each codon represents a particular amino acid in the polypeptide chain of a protein.
1. “Genetic code.” Nature News, Nature Publishing Group, Available here.
2. “How do genes direct the production of proteins? – Genetics Home Reference.” U.S. National Library of Medicine, National Institutes of Health, Available here.