Chapter 12 Flashcards
Describe the 3 possible models of DNA replication
Semiconservative- each strand used to make a new molecule
Conservative- New dna has 2 new molecules
Dispersive- Chunks of old and new DNA in new molecules
- Describe the Meselson & Stahl experiment and understand how they interpreted their results
Grew E coli in media with Heavy N isotope, saw that ratios of normal N decreased by 1/2 each generation
- Using the Meselson & Stahl experiment design, predict the results if DNA were replicated in a conservative
fashion or a dispersive fashion.
Dispersive
- Define dNTP
monomeric unit of DNA with a nitrogen base, bound to deoxyribose sugar, and three phosphate groups attached to its 5’ carbon
- List the 4 substrates required for DNA replication
- dATP, dTTP, dGTP, dCTP
- Briefly describe the 3 models of semiconservative replication
- Theta Model—common in bacteria
- Rolling Circle Model—some viruses and bacteria
- Linear Model—eukaryotic chromosomes
Explain how dNTPs are added to a growing DNA chain
DNA polymerase connects 5’ phosphate group of DNTP with 3’ hydroxyl group of previous nucleotide
- Know the direction of DNA synthesis
5’ to 3’
- Explain how 5’ to 3’ replication can occur simultaneously on two antiparallel strands
- nucleotides added to 3’ OH of growing chain, so chain grows in a 5’ to 3’ direction
- template strand is read in a 3’ to 5’ direction because it is antiparallel to the new strand
continuous DNA synthesis
No interruption to DNA synthesis (no okazaki fragments)
theta replication,
DsDNA unwinds, creating replication bubble looking like a theta θ
- Describe 3 sequential processes that lead to the accuracy of DNA replication
o nucleotide selection
o proofreading
o mismatch repair
- What are the steps for replication in bacteria?
Initiation, unwinding, elongation, termination
Explain how the telomeres are replicated with the help of telomerase
Telomerase complements 3’ overhand of strand and adds extra bases for the rest of the telomerase’s sequence. Complementary strand is filled in to save degraded DNA
What’s used to unwind DNA?
2) unwinding
– Helicase
– SSBs
– Gyrase (topoisomerase)
o DNA polymerase: requires ________ in order to _____________
3’ OH, add a nucleotide
When does termination happen in bacterial DNA replication?
Usually occurs when replication forks run into each other
o Primase:
creates primer (RNA) to initiate DNA synthesis
(Bacteria)▪ DNA Polymerase III -
synthesizes DNA from primers
(Bacteria)▪ DNA Polymerase I -
removes and replaces primers
(Bacteria)▪ DNA Polymerase II, IV, V -
DNA repair
▪ Primase =
Ligase
RNA polymerase; does not require 3’ OH
o ____________ origins of replication in eukaryotes
Multiple
(Eukaryote)
▪ DNA pol α:
has primase activity; initiates DNA synthesis
