Unit 8.2 Flashcards
What is the definition of leading strand?
The strand of DNA that is continuous and goes towards the replication fork.
What is the definition of lagging strand?
The strand of DNA that is discontinuous and points away from the replication fork.
What is the definition of Semi-discontinuous?
When something starts at different places on the strand and slowly replicates the DNA. It must make a small section then back up and do another. This means it cannot get it all in one go.
What is the definition of semi-conservative replication?
This is where each of the two daughter molecules will have one old strand front he parental molecule and one newly-made strand.
What is the definition of Okazaki fragments?
These are the fragments of the nuecleotides that must be connected by the ligase to create a whole strand of DNA.
What is the function of the enzyme Helicase?
It splits the DNA strands hydrogen bonds and unwinds it.
What is the function of the enzyme DNA polymerase 3?
It creates an identical strand by adding nucleotides to the primer and connects the base pairs.
What is the function of the enzyme DNA polymerase 1?
It removes the primers and replaces them with DNA nucleotides.
What is the function of the enzyme Ligase?
The ligase attracts the Okazaki fragments together to make the DNA strand whole.
What is the function of the enzyme Primase?
The primase adds RNA primers to the strand. These are needed because DNA polymerase can only add new nueceotides to an existing strand.
What is the order of events in DNA replication?
Helicase, Primase, DNA polymerase 3, DNA Polymerase 1, then Ligase.
Explain Meselson’s and Stahl’s experiment setup and what the results were.
They cultured E.coli in a medium containing nucleotides labeled with a heavy isotope of nitrogen. Then then transferred the bacteria to a medium with only a lighter isotope. A sample was taken after the DNA had replicated once and then again after it had replicated twice. They found that DNA replicates using the semi-conservative model because after the first replication they were mixed so they were in the middle of the tube. Then after the replicated twice there were some that were mixed, then some that was all light.
