![]() Mechanism to cut out and replace with correct basesġ4 Mutations A mismatching of base pairs, can occur at a rate of 1 per 10,000 bases. Ligase forms bonds between sugar-phosphate backbone.ġ3 Proofreading DNA must be faithfully replicated…but mistakes occurĭNA polymerase (DNA pol) inserts the wrong nucleotide base in 1/10,000 bases DNA pol has a proofreading capability and can correct errors Mismatch repair: ‘wrong’ inserted base can be removed Excision repair: DNA may be damaged by chemicals, radiation, etc. Discontinuous synthesis produces 5’ to 3’ DNA segments called Okazaki fragments.ġ1 Replication 3’ 5’ 5’ 5’ 3’ Exonuclease activity of DNA polymerase I removes RNA primers.ġ2 Replication 3’ 5’ Polymerase activity of DNA polymerase I fills the gaps. Discontinuous synthesis produces 5’ to 3’ DNA segments called Okazaki fragments.ĩ Replication 3’ 3’ 5’ 5’ 3’ 5’ 3’ 5’ 3’ 3’ 5’ 5’ġ0 Replication 3’ 5’ 3’ 3’ 5’ Leading strand synthesis continues in aĥ’ to 3’ direction. Okazaki fragment 3’ 5’ 3’ 5’ 3’ 5’ Leading strand synthesis continues in a 5’ to 3’ direction. Discontinuous synthesis produces 5’ to 3’ DNA segments called Okazaki fragments.Ĩ Replication Overall direction of replication 3’ 3’ 5’ 5’ Leading strand synthesis continues in a 5’ to 3’ direction. Leading strand synthesis continues in a 5’ to 3’ direction.ħ Replication 3’ 5’ Overall direction of replication Okazaki fragment DNA polymerase proofreads bases added and replaces incorrect nucleotides.Ħ Replication Overall direction of replication 3’ 5’ 3’ 5’ Helicase protein binds to DNA sequences called origins and unwinds DNA strands.Ĥ Replication Overall direction of replication 5’ 3’ĭNA polymerase enzyme adds DNA nucleotides to the RNA primer.ĥ Replication 5’ Overall direction of replication 3’ĭNA polymerase enzyme adds DNA nucleotides to the RNA primer. 5’ 3’ Binding proteins prevent single strands from rewinding. Primase adds short primer to template strand Helicase unwinds parental double helix Binding proteins stabilize separate strands DNA polymerase III binds nucleotides to form new strands DNA polymerase I (Exonuclease) removes RNA primer and inserts the correct bases Ligase joins Okazaki fragments and seals other nicks in sugar-phosphate backboneģ Replication Primase protein makes a short segment of RNAĬomplementary to the DNA, a primer. DNA polymerase III extends the strand in the 5’-to-3’ direction DNA polymerase I degrades the RNA primer and replaces it with DNA DNA ligase joins the DNA fragments into a continuous daughter strand Many proteins assist in DNA replication DNA helicases unwind the double helix, the template strands are stabilized by other proteins Single-stranded DNA binding proteins make the template available RNA primase catalyzes the synthesis of short RNA primers, to which nucleotides are added. ![]() Presentation on theme: "The Mechanism of DNA Replication"- Presentation transcript: ![]()
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