Ch 8 Genomes Flashcards
What is positive supercoiling?
DNA is overwound
What is negative supercoiling?
DNA is underwound
Who possesses negative supercoiling?
Eukaryotes, bacteria, and most archaea
Who possesses positive supercoiling?
Archaea living in acid at high temperatures
Which enzyme changes DNA supercoiling
topoisomerase
What does Type I topoisomerase do?
Cleaves on DNA strand and use single proteins (less negative supercoils)
What does Type II topoisomerase do?
Cleaves both strands of DNA, has multiple units
_________is an example of Type__ topoisomerase
DNA gyrase, II
What antibiotic targets DNA gyrase?
Quinolone
What is semiconservative DNA replication?
Each daughter cell receives one parental and one newly synthesized strand
Where does bacterial replication begin?
Origin (oriC)
Where does bacterial replication end?
Termination (ter) sites
What is DnaA?
The initiator protein
What is DnaB?
Helicase
What is DNA primase?
Synthesis of RNA primer
What is DNA Pol III?
A major replication enzyme
What is DNA Pol I?
Replaces RNA primer with DNA
What is DNA gyrase?
Relieves DNA supercoiling
What does the sliding clamp do?
Tethers DNA pol. to DNA so it doesn’t fall off
What is the leading strand?
Replicated continuously in the 5’-3’ direction
What is the lagging strand?
Replicated discontinuously in stages
What are Okazaki fragments?
Synthesized DNA fragments linked together by DNA ligase to form the lagging strand
What does the replisome do?
Makes sure that the leading and lagging strand go in the 5’-3’ direction
How to get rid of RNA primers?
RNase H
What does helicase do?
Temporarily separates double helix strands so DNA/RNA synthesis can occur
What do tus proteins do?
Act as a counter-helicase to stop DNA synthesis
What are ringed catenanes?
They form at the end of replication to be separated by topoisomerase IV
What are plasmids?
DNA molcs. that replicate independently
True or False: Plasmids can be resistant to antibiotics
True
True or False: Plasmids cannot be transferred amongst cells
False
What direction do plasmids replicate?
Bidirectionally and rolling-circle
True or False: Archaea replication resembles that of eukaryotic replication
True
