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28 Cards in this Set
- Front
- Back
Initiation
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Step One:
-DNA gyrase uncoils DNA molecule -Initiation occurs at specific site called oriC region which is rich in A's and T's which is easier to uncoil because they have double bonds not triple bonds Step Two: -Initiator proteins (SSBP) binds to DNA strand and stabilizes Step Three: Helicase unzips ds DNA by breaking H bonds |
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Elongation
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Step 4:
-Primase adds a 10-20 base pair piece (primer) of RNA to end of each ss DNA molecule -Multiple primers added to LAGGING strand -DNA replication occurs in 5' to 3' direction (3'---5' leading, 5'---3' lagging) Step 5: LEADING -DNA pol III binds to DNA at fork -Clamp and clamp loader lock enzyme onto DNA -DNA pol III slides down DNA strand toward 5' end adding nucleotides to complementary bases on template -H-bonds form between bases and phosphodiester bonds between sugars to make ds back bone Step 5: LAGGING -DNA pol III attaches to DNA and is clamped Step 6: -DNA pol III synthesizes Okazaki fragments -At end of each fragment it is released and reattaches to beginning of each fragment (5-->3 , 3<---5 harder) Synthesized in Okazaki fragments |
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Termination
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Step 7: DNA polymerase I removes primers, fills in gaps between fragments on lagging strand so have a complete strand
Step 8: DNA ligase connects all pieces together |
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DNA gyrase
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Relieves torque
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Helicase
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Unwinds the double helix by breaking H-bonds
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SSBP
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initiator proteins
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Primase
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Synthesizes RNA primers
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DNA polymerase III
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Synthesizes DNA
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Clamp and Clamp loader
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The beta subunit is made up of two identical protein chains that come together to form a circle, this circle can be loaded onto the template like a clamp.
Multisubunit protein called clamp loader accomplishes opening and closing the clamp around the DNA |
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DNA polymerase I
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Erases primer and fills gaps
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DNA ligase
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Joins the ends of DNA segments; DNA repair
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E. Coli
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-DNA is 1000x longer than cell
-30 miles fishing line into a blueberry -Supercoiling: twisted and packed to fit |
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oriC
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site where initiation occurs
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supercoiling
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twisting and packing DNA to fit into a cell
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Initiator proteins
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(SSBP) binds to DNA strand and stabilizes
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Replication fork
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The opening between two strands
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Primer
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10-20 base pair piece of RNA added to each end of ss DNA molecule
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Antiparallel
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3'--5'
5'--3' |
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Discontinuous
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The lagging strand
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Lagging strand
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-Discontinuous
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Leading strand
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Continuous
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Okazaki fragments
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DNA fragments synthesized on the lagging strand. They introduce a need for even more enzymatic activity on lagging strand
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What are the 3 main events in DNA replication?
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Initiation
Elongation Termination |
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What enzymes are required for DNA replication?
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Helicase, primase, SSBP, DNA gyrase, DNA pol III, DNA pol I, DNA ligase
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template
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The parental DNA strand serves as the template to be copied by the enzymes
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replisome
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Enzymes involved in DNA replication forms macromolecular assembly called the replisome.
-Replication organelle -Contains all necessary enzymes for replication |
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What is supercoiling and why is it needed?
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Supercoiling is the twisting and packing of DNA to fit within a cell
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What chemical bonds are formed during elongation?
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During elongation, Hydrogen bonds are formed between bases (double between A and T, triple between C and G) and phosphodiester bonds form between the sugars to make the ds backbone
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