Information Flow from DNA to RNA to Protein

tRNA charger protein

A tRNA has a specific charger protein called aminoacyl tRNA synthetase which can only bind to a particular tRNA and attach the correct amino acid to the acceptor site.

DNA transcription

Definition: Synthesis of RNA from a DNA template. The most important enzyme is RNA polymerase.

Codon

Each codon specifies a particular amino acid, hence the ribosomal complex builds a protein one amino acid at a time, with its order determined precisely by the order of codons in mRNA.

Transcription Process

In order for transcription is to initiated, RNA polymerase must first be able to recognise the beginning sequence of a gene, so that it knows where to start synthesising the mRNA. Once at the initiation site, the RNA polymerase then unwinds the double helix and begins the synthesis of an RNA strand (template strand/antisense) complementary to a strand of DNA (coding strand/sense). Synthesis can then proceed in a unidirectional.

Ribosomes

Ribosomes are responsible for synthesising proteins. The ribosome consists of a structural RNA and about 80 different proteins. In its inactive state, it exists as two subunits - the large subunit and the small subunit. When the small subunit encounters an mRNA, the process of translating an mRNA begins. In the large subunit, there are 2 sites for amino acids to bind which allows them to firm binds.

"A site"

The "A site" accepts a new mRNA, which bears an amino acid and is the adaptor molecule acting as a translator between the mRNA and protein.

"P site"

The "P site" binds the tRNA that becomes attached to the growing chain.

Central Dogma

The central dogma states that genetic information flows from the DNA to the RNA to the protein. The genetic code reside in DNA is passed from generation to generation.

Exons & Introns

The coding portion of the gene called exons are interrupted by intervening sequences called introns. Both exons and introns are transcribed into mRNA, but before being transported to the ribosome, the primary mRNA transcript is edited. The editing process removes the introns, joins the exons together and adds in a unique feature to each end of the transcript to make a mature mRNA.

tRNA acceptor site

The tRNA is a specific RNA molecule. Each tRNA has a specific acceptor site that binds a particular triplet of nucleotides, codon and an anticodon site that binds a sequence of three unpaired nucleotides, anticodon which can then bind to the codon.