Dna Replication Class Notes For Biochemistry

The central dogma of molecular biology describes the flow of information beginning with genes in cells. A human has 46 chromosomes. DNA replication is a semi conservative process. This was proved by an experiment done by messelson and stahl. Each polynucleotide strand acts as a template for base-pairing to form a complimentary strand. (ATGC)DNA replication only works in the 5’ 3’ directionUses ssDNA (single stranded) as templates to synthesize a complementary DNA strandIncoming nucleotides must form Watson-Crick basepairs w/ the templatePhosphodiester bonds link nucleotidesRequires an RNA primer to provide a free 3’-OH group- primer is synthesized by RNA pol or Primase (dnaG)Cannot initiate DNA synthesis from free nucleotidesReplication is semi-discontinuous.Since DNA polymerase works in the 5’ to 3’ direction, the leading strand can synthesise a continuous new strand of DNA, whereas the lagging strand cannot. Hence the lagging strand synthesises DNA discontinuously known as Okazaki fragments. Three types: Pol I, Pol II, Pol IIIAll three have 5’ 3’ polymerase activityPol III DNA replication (1000 nt/sec)All have 3’ – 5’ exonuclease activity; excises an incorrect nt. at the end of a growing