BIOCHEM 2EE3 Lecture 9: Module 5
8 Dec 2017
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Document Summary
Rna primer (orange arrows: okazaki fragments -> small fragments of dna (many of them along the lagging strand) these fragments are covalently linked together by dna ligase once the rna primers have been hydrolyzed and replaced with dna. There are multiple dna polymerases are found in cells. Of these there are three key enzymes in e. coli: pol i, pol ii and pol iii. Pol i and pol ii are involved in dna repair. Pol i is also utilized in dna replication. Nucleases are enzymes that catalyze the breakdown of dna or rna into smaller fragments and/or nucleotides. An exonuclease catalyzes cleavage of nucleotides from the end of a dna or rna polymer. The exonuclease activity removes incorrectly matched bases, so that the polymerase can try again. For example: dna polymerase i possesses the following nuclease activities: A 3" 5" (reverse) exonuclease activity that mediates proofreading. A 5" 3" (forward) exonuclease activity mediating nick translation during dna repair.
