DNA Replication machinery can be understood in following sections-
- Activation of Deoxyribonucleotides: Four nucleosides of DNA i.e. AMP,GMP, CMP, and TMP are found floating Free in nucleus .All of these are activated by ATP to from deoxyribose Nucleoside triphosphatases called ATP,GTP.CTP & TTP. Enzyme required at this Step is the phosphorylase and step is called phosphorylation.
- Recognition of Initiation point: The specific point from where unwinding of DNA start is called initiation of DNA Replication. In prokaryotes as the bacteria etc there is one initiation Point but in eukaryote there are many initiation points of replication. These are identifying by initiator proteins. Which (Initiation points of eukaryotes) finally merges with one another.
- Unwinding of DNA Molecule: The DNA double helix unwind to from single strands of DNA by the breakdown Of Hydrogen bond enzyme Helicase help in unwinding of duplex. Topoisomerases cut and rejoin one strand of DNA helping the separation Of DNA helix. This helps to remove the twists of DNA and thus relieves the Tensions of DNA and separated its strands. This unzipping of double stranded DNA form the replication bubble now it extends as Y- shaped structure that Called replication fork
- Formation of DNA primer: DNA directed RNA polymerase forms the RNA primer. It is comparatively easier to add on already existing small chain primer formed from DNA Template. This is accomplished by the synthesis of a short segment of RNA Primer. RNA primer is ultimately removed enzymatically leaving a gap in newly Synthesized deoxyribose nucleotide strand. This gap must be filled in.
Formation of New DNA chains
Enzyme DNA polymerase can polymerase the nucleotides only in 5’-3’ direction. DNA polymerase is responsible for the template directed condensation of Deoxyribose nucleotide triphosphatases. Synthesis of new (Template) Complementary strand proceed from 3’ OH terminus of primer causing Growth in 5’-3’ direction.
Addition of deoxyribonucleotides is done by DNA Polymerases’ in presence of ATP. Enzyme synthesizes a new strand of DNA In a continues form 5’—3’ direction and is called as the leading stand. On the Other hand. The enzyme forms the discontinues strand in the direction of 5’—3’initiating form RNA primer. Primer is formed with primase enzyme. Small Segment called okazaki fragment. This is called as lagging strand.