Protein synthesis is the process of transferring information from a gene to a protein. DNA (Deoxyribonucleic acid) is made up of four main parts of adenine, thymine, guanine, and cytosine, and RNA (Ribonucleic acid) is made up of adenine, uracil, guanine, and cytosine. DNA is a double, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell's proteins. RNA is a single-stranded nucleic acid molecule involved in protein synthesis, the structure of which is specified by DNA. Protein synthesis consists of two main categories: transcription, which is the process of copying RNA information to DNA, and translation, which is the process of turning RNA information to DNA.
Transcription is the process of copying DNA information to RNA. It begins at the initiation site when the polymerase separates the two DNA strands and exposes the template strand for base pairing with RNA nucleotides. The RNA polymerase works its way down from the initiation site, prying apart the two strands of DNA and elongating the mRNA in the 5' Ã 3' direction. The entire stretch of DNA that is transcribed is called a transcription unit. The RNA polymerase continues to elongate the RNA molecule until it reaches the termination site, a specific sequence of nucleotides along the DNA that signals the end of the transcription unit. The mRNA, a transcript of the gene, is released, and the polymerase subsequently dissociates from the DNA. .
Translation is the process of turning RNA information to DNA. First, a small ribosomal subunit binds to a molecule of mRNA. The positioning of the mRNA is signaled by a ribosome recognition sequence of the mRNA. At the same time, the initiator tRNA, with the anicodon UAC, base pairs with the initiation codon AUG. This tRNA carries the amino acid methionine (Met). Then the large ribosomal subunit joins the initiation complex. The initiator tRNA is in the P site.