Ncert plus two biology surendran aduthila

1. DNA Replication

2. Watson and Crick 1953 article in Nature

3. Double helix structure of DNA “ It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” Watson & Crick

7. Bonding in DNA … . strong or weak bonds? How do the bonds fit the mechanism for copying DNA? 3  5  3  5  covalent phosphodiester bonds hydrogen bonds

11. DNA-pol of eukaryotes DNA-pol  : elongation DNA-pol III DNA-pol  : initiate replication and synthesize primers DnaG, primase DNA-pol  : replication with low fidelity DNA-pol  : polymerization in mitochondria DNA-pol  : proofreading and filling gap DNA-pol I repairing

19. Replication fork / Replication bubble leading strand lagging strand leading strand leading strand lagging strand DNA polymerase III 5  3  5  3  5  3  3  5  5  3  5  3  5  3  5  3  growing replication fork growing replication fork 5  5  5  5  5  3  3  5  5  5  3 

25. What does it really look like? 1 2 3 4

28. Semiconservative replication Half of the parental DNA molecule is conserved in each new double helix, paired with a newly synthesized complementary strand. This is called semiconservative replication

29. Semiconservative replication

30. Experiment of DNA semiconservative replication

33. Replication fork

35. Bidirectional replication

36. Replication of prokaryotes The replication process starts from the origin, and proceeds in two opposite directions. It is named  replication.

38. origins of DNA replication (every ~150 kb)

40. On the template having the 3´- end, the daughter strand is synthesized continuously in the 5’-3’ direction. This strand is referred to as the leading strand . Leading strand

41. Semi-continuous replication

43. Continuous synthesis of the leading strand and discontinuous synthesis of the lagging strand represent a unique feature of DNA replication. It is referred to as the semi-continuous replication . Semi-continuous replication

44. Any Questions??