Define Semi-conservative, conservative and dispersive
Semi: each parent strand serves as a template for a new strand and the new and old combine to make the new strand
conservative: the double helix services as a template for a new double helix but doesn't contribute
Dispersive: fragments of the original DNA molecule serve as a template for assembling two new molecules each containing old and new parts.
The Meselson-Stahl Experiment
-to determine which hypothesis of DNA replication was correct
-found that DNA replication was semiconservative- each newly made DNA molecule comprises one old and one new strand If dispersive, same heaviness. If semiconservative, First HL, then LL in later generations, if conservative then always LL.
Where does replication start and how does it continue?
Always happens in 5' -> 3' direction, and starts replication bubble from origin of replication and adds DNA outwards from bubble
Leading strand - DNA replication is constant Lagging strand - DNA replication is made in fragments Fragment amounts decreased as replication proceeded. These fragments are called Okazaki fragments The 3' -> 5' direction is synthesized from 5'-> 3' in fragments
DNA replication uses RNA primers. Why?
DNAP cannot make a new DNA from "nothing", it can only extend from existing DNA or RNA. This existing DNA/RNA fragment is called a primer.
RNA primers contain more errors so its removal is certain, or RNAP needs no primer can explain why RNA primers are used.