DNA is found in chromosomes. In eukaryotic cells, chromosomes always remain in the nucleus, but proteins are made at ribosomes in the cytoplasm. How do the instructions in DNA get to the site of protein synthesis outside the nucleus? Another type of nucleic acid is responsible. This nucleic acid is RNA or ribonucleic acid. RNA is a small molecule that can squeeze through pores in the nuclear membrane. It carries the information from DNA in the nucleus to a ribosome in the cytoplasm and then helps assemble the protein. The central dogma of molecular biology is an explanation of the flow of genetic information within a biological system. It is often stated as "DNA makes RNA, and RNA makes protein".

Central Dogma steps

1. Replication

DNA must be duplicated in a process called replication to give identical copies before a cell divides. The replication of DNA allows each daughter cell to contain a full complement of chromosomes. This process perpetuates the genetic information.

2.Transcription

Transcription is the process by which the information is transferred from one DNA strand to RNA by RNA Polymerase. The DNA strand which undergoes this process consists of three parts namely promoter, structural gene, and a terminator. The DNA strand that synthesizes the RNA is called the template strand and the other strand is called the coding strand. The DNA-dependent RNA polymerase binds to the promoter and catalyzes the polymerization in the 3′ to 5′ direction. As it approaches the terminator sequence, it terminates and releases the newly synthesized RNA strand. The newly released RNA strand further undergoes post-transcriptional modifications.

3.Translation

Translation is the process by which the mRNA codes for a particular protein. Ribosomes initiate the translation process. The ribosomes consist of a larger subunit and a smaller subunit. The larger subunit, in turn, consists of two tRNA molecules placed close enough so that a peptide bond can be formed at the expense of enough energy. The mRNA enters the smaller subunit which is then held by the tRNA molecules of the complementary codon present in the larger subunit. Thus, two codons are held by two tRNA molecules placed close to each other and a peptide bond is formed between them. As this process repeats, long polypeptide chains of amino acids are synthesized. In the process, the ribosome translates the mRNA produced from DNA into a chain of specific amino acids. This chain of amino acids leads to protein synthesis. It is a process where the expense of ATP is required and this energy is given by the charged tRNA. The whole machinery of translation is present in the ribosomes.

DNA → mRNA → Protein