6080946
Description
Flashcards by Emma Allde, updated more than 1 year ago
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Created by Emma Allde
over 8 years ago
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| 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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