Genetic 342 A&B Kenneth G Wilson Professory of Botany

Replication of DNA

• Enzymology - Art Kornberg

Three possible models for semiconservative replication of DNA.

Test of models using Tritiated [3H] thymidine

How could you use the above model to measure the rate of DNA synthesis?

Now let us look at a model to explain the rest of the data.

The replication bubble in Drosophila embryos

The system is very similar in E. coli

Bidirectional replication of circular molecules give rise to theta structures and finally two circles

 

Origin	Growing Regions	Structure	Results
Two	Two	Ends	No
One	One	Forks	Very Rare
One	Two	Forks	Common

General Scheme for DNA replication

• Initiation - Start of macromolecular syntheses (N - (N-1) ) -

  • Starts with a bubble and RNA Primers

  • RNA Primers are removed by pol1

  • DNA pieces are ligated together

  • Flash Summary

• Elongation - step by step addition of Nucleotides (N-2)

  • RNA Primers are removed by pol1

  • DNA pieces are ligated together

  • Flash Summary

• Termination - stop of replication (N - (N-1) )

  • What happens at the "End"?

In vitro Enzymatic Replication of DNA

Chemistry of Chain elongation reaction catalyzed by DNA Polymerase.

Model for bidirectional migration of two forks

Origin of Replication - OriC

Origins of replication in E. coli

Autonomous Replicating Sequences in Yeast

Initiation of Replication

Model from text

 What does it mean to prime the pump?  

      Primase starts the synthesis of DNA

Both strands are both Leading and Lagging

The structure of the growing forks

Ligase hooks things together

How can the polymerase go both directions at once ?

Lets look at a model to explain this part a, part b, and summary

This is our friend Oliver the parrotlet, Oliver is a true parrot, the smallest in the world.