Proteins play a vital role within the cell by serving as the structural, functional, and regulating molecules. Various types of proteins required for the function of a cell are synthesized within the cells. The information for the synthesis of these proteins is encoded within the genome. The genetic material of most organisms is DNA. DNA is made up of nucleotides. A nucleotide triplet that represents a particular amino acid of a protein is known as a codon. The set of rules by which the genetic information is encoded within the genetic material is known as the genetic code. A sequence of codons within the genome is known as a gene that codes for a particular functional protein within the cell. Hence, a genome should consist of a number of protein-coding genes. The genome is also encoded for various types of functional RNA molecules.
Key Areas Covered
Key Terms: Amino Acid, Codon, Genetic Code, Protein, RNA, Transcription, Translation
What is a Genetic Code
The genetic code is the set of rules by which the genetic information is encoded within the genome. The genes of the genome are made up of a series of nucleotides that can be grouped into codons. The genetic code links the set of codons within a particular gene into either the amino acid set of the polypeptide chain of a protein or the RNA codon sequence of functional RNA molecules such as tRNA and rRNA. The genetic code consists of sixty-four codons that represent unique amino acids that are involved in protein synthesis. The genetic code that represents the 20 amino acids is shown in figure 1.
Degeneracy is one of the significant features of the genetic code. This means a single amino acid can be represented by more than one codon. The genetic code does not overlap; a single nucleotide cannot be a part of two adjacent codons, and the genetic code is nearly universal.
How Does DNA Encode Information
The genetic code defines how the four types of nucleotides of DNA are translated into the twenty amino acids involved in the protein synthesis. The two steps of protein synthesis are transcription and translation. During transcription, the DNA genetic code is transcribed into RNA genetic code. Three types of RNAs are produced during transcription are mRNA, tRNA, and rRNA. The RNA codon sequence of the mRNA is translated into the amino acid sequence of a protein. Each amino acid of the protein is represented by a particular codon. Generally, twenty amino acids are involved in protein synthesis, and they are represented by sixty-one codons. Three codons serve as stop codons that terminate the transcription. An overview of protein synthesis is shown in figure 2.
tRNAs and rRNAs serve as functional molecules of protein synthesis. tRNAs bring the corresponding amino acids during translation while rRNAs serve as functional parts of the ribosome that facilitates translation.
The genome, which is mainly made up of DNA, is encoded for information for both protein synthesis and RNA synthesis. The coding regions of the genome are known as genes. Genes are made up of a series of codons that consist of groups of three nucleotides. Each codon represents a particular amino acid of the polypeptide chain of a protein or RNA codons of a tRNA or rRNA.
1. “DNA Is a Structure That Encodes Biological Information.” Nature News, Nature Publishing Group, Available here.
1. “Translationchart” By Gurustip at English Wikibooks – Transferred from en.wikibooks to Commons by Adrignola (Public Domain) via Commons Wikimedia
2. “Overview of Protein Synthesis” by Becky Boone (CC BY-SA 2.0) via Flickr