DNA Replication

Types of DNA Structure Type of Cell Structure of DNA What the replication structure is called Prokaryote Double stranded circle Replication Bubble Eukaryote Double stranded linear Replication Fork

Steps of DNA Replication # Step Enzyme/Protein 1 Unwind the double helix and separate the strands -break the H bonds between the Nitrogenous bases Helicase 2 Relax the front of the helix where it is tightening up due to the unwinding Topoisomerase /DNA gyrase 3 Stabilize the DNA so it can allow the DNA polymerase to bind SSBPs-single stranded binding proteins 4 Add an RNA Primer or platform to give the DNA polymerase a place to add DNA nucleotides (the 3’-OH is sticking out so the DNA pol can add the 5’-P end of the new nucleotide to it) Primase

Steps of DNA Replication # Step Enzyme/Protein 5 DNA polymerase III adds new nucleotides to the parent strands DNA polymerase III 5A Leading or Continuous strand-Forward in the 5’ to 3’ direction. Moves quickly 5B Lagging or discontinuous strand-DNA pol III moves backwards in short burst. Multiple primers made. Small fragments called Okazaki fragments are made. Moves more slowly 6 The RNA primers have to be removed and replaced with DNA nucleotides. DNA polymerase I 7 The gaps in the Sugar-Phosphate backbone have to ligated or stitched back together from where the RNA primers were and to stitch together the Okazaki fragments. Ligase

DNA Replication Video https://www.youtube.com/watch?v=JZXT2uOcD2w DNA replication goes in the 5’ to 3’ direction