![]() But even more enthralling is its ability to self-replicate and generate another molecule similar to itself. The simple chemical code of the DNA molecule gives rise to the immense complexity of all living organisms. With this foundation, and the research by several scientists like Rosalind Franklin, the structure of this molecule was finally deciphered by James Watson and Francis Crick. It took several interesting experiments by Frederick Griffith, Avery, MacLeod, McCarty, Alfred Hershey, Martha Chase etc., to discover that DNA is the hereditary material. This is equivalent to copying 100 dictionaries (with 1000 pages each) word to word, page to page, and symbol to symbol, with only one mistake!ĭeoxyribonucleic acid or DNA is the fascinating molecule that stores and passes all the necessary information from one generation to another. This process is known as decatenation.Less than one mistake occurs while copying a billion nucleotides. Finally DNA topoisomerase IV cuts one DNA, removes it out of other and finally reseals it. Such interlinked DNA are called catenanes. Therefore two interlinked daughter DNA are obtained at completion of replication. When two replication fork meets Ter-Tus complex, DNA synthesis stops.Replication must be terminated to produce two daughter DNA molecule and to regulate and co-ordinate replication with cell division.After completion of chain elongation RNA primer is removed by exonuclease activity of DNA polymerase I and the gap is filled with complementary bases.Since the direction of movement of replication fork is opposite to direction of lagging strand synthesis, it cannot be synthesized continuously. DNA ligase joins these Okazaki fragments to form complete lagging strands. Due to discontinuous formation, smaller fragments are formed, which are called Okazaki fragments. However, in other template strand 5’→3’, there is discontinuous formation of DNA and thus more RNA primer are required for the formation of whole strand.Since the direction of movement of replication fork and direction of leading strand synthesis are same, leading strand is synthesized continuously after its initiation. The continuous strand of DNA is called leading strand. DNA Polymerase III forms continuous strand of DNA on 3’→5’ template.Chain elongation proceeds from the initiation site by the addition of deoxyribonucleotides at 3’-OH end of the primer by DNA polymerase III.Initiation of replication requires RNA primer, which is a small strand of RNA, synthesized by primase. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |