In this lecture you will learn:
DNA is the master copy of all the genes that build and run each cell. Every cell in the body has its own copy of DNA. When it is time for a cell to split into daughter cells, a new copy of DNA must first be made and that process of duplicating the DNA is called REPLICATION
DNA REPLICATION MOVIE
|Replication occurs at multiple sites of double DNA strands|
|1. Topoisomerase initiates the unwinding of the DNA supercoil by briefly cutting a strand so the DNA can unwind.|
|2. Helicase unwinds the double strand and melts the hydrogen bonds holding the bases together (needs ATP to function)|
DNA replication with a small RNA primer that has an - OH for DNA polymerase
The RNA primer is later removed by RNase and the gap is filled in by DNA polymerase I.
(III- major polymerase)
It binds to one side of the DNA and guides nucleotides to bond with their complementary
It mediates formation of the covalent phosphodiester bond on the 5' end
It has proofreading and nuclease activity to cut away mistakes
|5. Ligase is an enzyme that can catalyze a phosphodiester bond to fill in a gap left when the RNA primer is removed and filled in.|
|2 diagrams of DNA replication
Enzymes are proteins that are organic catalysts. They basically they make reactions occur that would not occur fast enough normally. They do this by lowering the energy of activation. Enzymes often have co-enzymes or factors.
WATCH ANIMATION OF HOW ENZYMES WORK HERE
|Enzymes bring substrates together by binding to one or more of the reactants to an active site thru hydrogen bonds. The shape of the active site just fits the shape of the substrate, somewhat like a lock fits a key. The enzymes often undergo a conformational change when they mediate the reaction.|
|The reaction can be affected by temp and/or
pH as enzymes have an optimal temp and pH at which they work the best.
They also have temp and pH where they wont work.
hold down shift and then reload to see animation
What is the purpose of replication?
Describe the 5 steps involved in DNA replication.
What are the characteristics of enzymes?