DNA replication Flashcards
What is meant by “semiconservative” DNA replication?
Each new DNA molecule contains one ‘old’ (template) strand and one newly synthesized strand.
What is the shape of prokaryotic DNA?
Circular and relatively small.
How many origins of replication do prokaryotes have?
A single origin of replication.
How fast can prokaryotic DNA replicate?
Up to 1000 nucleotides per second, completing replication in less than 40 minutes.
What is bidirectional replication?
Two replication forks move in opposite directions from the origin.
What is the shape of eukaryotic DNA?
Linear and large, organized into chromosomes.
How many origins of replication do eukaryotes have?
Multiple origins across each chromosome.
What influences the starting points of DNA replication in eukaryotes?
Chromatin state and epigenetic markers.
What are the three main steps in DNA replication?
Initiation, Elongation, and Termination.
What enzyme unwinds DNA during initiation?
DNA helicase.
What prevents DNA strands from reannealing during replication?
Single-strand binding proteins (SSBPs).
What relieves torsional strain in DNA during replication?
Topoisomerases.
What is origin licensing in eukaryotic replication?
Loading of helicases onto DNA by a conserved protein complex at potential replication sites.
What is origin firing?
Activation of selected licensed origins to initiate replication forks.
Why is origin firing selectively regulated?
To prevent replication stress due to limited resources or external stressors.
In what direction does DNA polymerase synthesize DNA?
5ʹ to 3ʹ direction.
Why does DNA polymerase need a primer?
It cannot start a new strand; it needs a free –OH group provided by a primer.
Which enzyme synthesizes the RNA primer?
Primase.
Which strand is synthesized continuously?
The leading strand.
Which strand is synthesized discontinuously?
The lagging strand.
What are the short fragments on the lagging strand called?
Okazaki fragments.
What is the approximate size of Okazaki fragments in prokaryotes?
~1000–2000 base pairs.
What is the approximate size of Okazaki fragments in eukaryotes?
~100–200 base pairs.
What removes RNA primers in prokaryotes?
DNA polymerase I.
