Th2L02 DNA replication


Medicine Y1 (Theme 2 | Genetics) Flashcards on Th2L02 DNA replication, created by Emma Allde on 20/08/2016.
Emma Allde
Flashcards by Emma Allde, updated more than 1 year ago
Emma Allde
Created by Emma Allde over 7 years ago

Resource summary

Question Answer
What happens during G1 phase Synthesis of protein components necessary to complete the cell cycle including histones, enzymes for replication, etc
How long does G1 phase take Takes 6-9 hours
What are the three main steps of DNA replication • DNA unwinds • Daughter strands of DNA produced from parent strand at replication fork Semi conservation replication (each new DNA molecule contains one parent and one daughter strand)
What enzyme is able to separate the two strands of DNA helicase
Replication occurs in what direction along parent strand 3' to 5'
New daughter strand is formed in what direction 5' to 3'
What is the Leading strand and by what means does it replicate The new continuous complementary DNA strand synthesised along the template strand in the mandatory 5' to 3' direction.
What is the Lagging strand and by what means does it replicate A discontinuously synthesised DNA strand that elongates by means of Okazaki fragment Each synthesised in a 5' to 3' direction away from the replication fork.
What are Okazaki fragments Small fragments of DNA produced on the lagging strand during DNA replication
How are Okazaki fragments joined together DNA ligase
What is Single strand binding protein (SSB) Enzyme Bind to and stabilize single strand of DNA until it can be used as a template Prevents DNA from clamping shut
What is the function of pulling strands apart Increases their winding about each other further down the molecule
What is positive super-coiling Compensates for strand separation
What is the role of DNA polymerase add nucleotides to pre-existing chains, making replication primed
What is the role of primase Synthesise short RNA stretches into primers so synthesis can begin without an existing DNA strand
What is the role of DNA polymerase III • Extends the primers with DNA NB: acts on lagging strand simultaneously and moves in the same direction as the replication fork
What is the role of DNA polymerase I Removes the RNA, and replaces it with DNA leaving a gap between adjacent fragments
What is the role of Topoisomerase cuts one or both strands of DNA to relieve the excess tension caused by the unwinding of the helix by helicase during replication (aka supercoils) preventing toxic DNA strand breakage
What is the role of DNA ligase Seals the gap between adjacent Okazaki fragments left by DNA polymerase I
In what direction does DNA ligase work and what kind of bonds does it make • Makes 5' to 3' phosphodiester bond Joining the adjacent fragments
What is the lagging strand template Looped to coordinate leading/lagging strand synthesis so that replication occurs in the same direction (towards the inside of the fork)
What is the sliding clamp A protein that holds DNA polymerase III in place by tethering it to DNA
How many replication origins are their per prokaryotic chromosome One
How many replication origins are their per eukaryotic chromosome Multiple
What is the distance between origins of replication in eukaryotic chromosomes 150k bp
What direction does replication occur it is bi-directional
What are intiator proteins Aid with the opening of double helices to form replication bubbles
What is the approx. number of nucleotides in the human genome 6 billion
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