Chapter 11- DNA Replication Flashcards
What is the correct model of DNA replication?
semiconservative model
Describe the semiconservative model
replicated DNA will have one old and one new strand of DNA
Describe the conservative model
the two parent strands rejoin
Describe the dispersive model
each strand is a mix of old and new
Describe origins of replication
where the two DNA strands are separated forming a “bubble”.
Describe the replication fork
the ends of the bubble where new DNA strands begin elongating.
Bacterial DNA is what shape?
circular
Describe helicases
enzymes that untwist the double helix at the replication forks
Describe topoisomerase
goes ahead of replication forks, cuts, unwinds, and rejoins DNA strands
Why is topoisomerase needed?
to keep the DNA strands from being too twisted
Describe single-strand binding protein
holds the DNA strand straight so it can be used as a template
What is a primer
a short strand of RNA that is laid down at the origin of replication
What is primase?
enzyme that lays down the primer
Describe DNA Polymerase III
adds DNA nucleotides to the 3’ end of the primer
The new strands grow in ________ directions.
opposite
DNA polymerases add nucleotides only to the __ ___of a strand
3’ end
a new DNA strand can elongate only in the __ to __ direction
5’ to 3’
Leading strand grows _______the origin of replication
in front of
Lagging strand grows _______ of the origin of replication
behind
Describe Okazaki fragments
a series of primers and new DNA segments
Describe DNA polymerase I
removes the RNA primers and replaces them with DNA nucleotides
Describe DNA ligase
connects the new DNA nucleotides