The various steps in the transcription and translation process of protein synthesis are described below.
Explanation:
Proteins (made up of amino acids) have an important role in the various functioning process of an organism. Protein synthesis which takes place in the cells of an organism consists of two major processes: transcription (DNA to RNA) and translation (RNA to protein).
Transcription: It is the first process in protein synthesis which occurs in the cell nucleus where a single-stranded messenger RNA (mRNA) is created using a DNA strand and the genetic instructions in DNA are transferred to this mRNA. The steps in transcription are initiation, elongation, and termination. The beginning process known as initiation occurs when an enzyme RNA polymerase binds to a promoter (region of a gene) and the DNA unwinds. One of the DNA strands acts as a template and the enzyme reads the bases in the template DNA strand.
The next step is elongation, where the RNA polymerase builds a strand of mRNA by the addition of nucleotides using complementary base pairs. Here, adenine (A) in the DNA binds to uracil (U) in the RNA. Termination is the last step in which the transcription process ends when the RNA polymerase comes across a termination sequence in the gene. Thus, the completed single-stranded mRNA detaches from DNA.
Translation: It is the second process in protein synthesis which occurs in the ribosome of the cell where the genetic information in mRNA is used to create a protein from amino acids. A triplet of nucleotides is called a codon and they define amino acids. There are 64 possible codons and the codon, AUG acts as the start codon which initiates translation in addition to specifying the amino acid methionine. In the initiation step, the first amino acid in the polypeptide chain is brought by transfer RNAs (tRNAs) to bind to the start codon of mRNA. During elongation, each type of tRNAs in the cytoplasm bound to a specific codon on the mRNA template and adds the corresponding amino acid to the polypeptide chain. Stop codons (UAA, UAG, or UGA) terminate protein synthesis and release the polypeptide.
