DNA REPLICATION

Process Of  DNA Replication

There are five step process of DNA Replication :

1. SEPARATION OF DNA DOUBLE HELIX 

•  DNA Helicase binds to origins cause the DNA double helix to unwind. The H bond between nitrogenous bases break causing DNA strand to separate . Each strand serves as a template. Replication occurs from 5' to 3' end . 

• Single-Strand Binding Proteins ( SSBP ) are  functional as prevent the DNA strands from rejoining .

• Topoisomerase are functional as relieves strain due to supercoiling of DNA molecule form.

     2.  BUILDING A PRIMER

• RNA  Primase adds a short RNA Primer and used as the primer for DNA Synthesis

      3. ASSEMBLING A COMPLEMENTARY STRANDS

• DNA Polymerase III add DNA Nucleotide to the RNA Primer .
• The free nucleotides pair up with the complementary bases in the parental DNA strand
• Base adenine pairs with thymine and cytosine pairs with guanine. 

• DNA Synthesis in continuous manner towards the replication fork is called leading strand while the other strands , DNA is discontinuously away from replication fork is called lagging strand .

• Produces  short fragments called Okazaki fragment 

     4. REMOVING THE PRIMER

• DNA Polymerase I   remove RNA Primers and replaced by DNA nucleotide .

     5. JOINING THE OKAZAKI FRAGMENTS  

• DNA Ligase catalyzes the formation of a phosphodiester bond between two Okazaki fragments
• Two identical strands of DNA are formed .