Wednesday, November 20, 2013

DNA Replication


DNA replication is a process in which two identical copies are created from one original DNA molecule. This process occurs in all living organisms and provides the basis for inheritance. It is a semiconservative process, meaning that each original serves as a template for the production of a complementary strand. 

The origin of replication is called promoter. The replication fork is created by helicase, which breaks the strands into two parts by breaking hydrogen bonds between nucleobases. There are two parts of each strand, the leading strand and the lagging strand. Then, RNA Primase comes in to create RNA that has a polar 3’ end. Its job is to help DNA polymerase read since DNA polymerase is polar. DNA polymerase III creates new nucleotides for the new strand of DNA. The bond in between the bases is a phosphodiester bond. It is important to distinguish that DNA is read from 3’ to 5’, but its synthesized from 5’ to 3’. Afterwards, DNA Polymerase I comes to replace RNA with DNA. However, the bond between these replaced DNA nucleotides is still incomplete. These nucleotides are known as Okazaki fragments. Finally, ligase glues DNA nucleotides together by phosphodiester bonds. This is the process of DNA Replication.

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