• Chromatin assembly factor (CAF-1) brings histones to the newly synthesized DNA. The nucleosomes bound to the parental strand are randomly dispersed among the daughter strands.
• The eukaryotic sliding clamp is called proliferating cell nuclear antigen (PCNA，增值细胞核抗原) is the site of CAF-1 binding.
ChargafBiblioteka ’s Rule• Erwin Chargaff showed that there was an approximate equality between the molar amounts of adenine and thymine as well as cytosine and guanine.
polymerase
III
molecules, along with
the sliding clamp
(PCNA) is called the
replisome.
• Note that we are looking at DNA replication in E. coli.
• The clamp increases the processivity of the DNA polymerase.
Replication
• There are three fundamental models for the mechanism of DNA replication.
• The mechanism suggested by the structure of DNA is the semiconservative model.
DNA Replication - DNA gyrase
• DNA gyrase （促旋酶）acts to change the supercoiling of the DNA.
DNA Replication - Eukaryotes
• Nucleosomes are made up of histones, highly conserved basic proteins specific to eukaryotes.
DNA Replication - The Replisome (复制体)
• Putting the molecules
that are involved in
DNA
replication
together, we get a
picture like this.
• The cooperating DNA
DNA Basic Structure
The Basis of Replication
• Each strand of DNA contains all of the information of the double helix. This allows the replication of DNA by separating the strands and using that information to synthesize novel strands.
• Remember, the outside of the double helix is the sugarphosphate backbone. The nitrogenous bases are on the inside of the double helix.
• Note the existence of the major groove and the minor groove on the double helix. DNA binding proteins can contact the bases through the major groove.
• However, the solution of the structure did not prove that DNA replicated in a semiconservative manner, and either the conservative or dispersive model could have explained the process of replication instead.
• This did not prove that A base pairs with T or that G bases pairs with C.
Waston
Crick
DNA Basic Structure
• The basic double helical structure of DNA is the basis for both DNA replication and transcription.