DNA replication (younger) Flashcards
DNA replication is ____________ and _____________.
Bidirectional and semiconservative
Replication begins in the interior of a DNA molecule and proceeds in both directions.
Bidirectional
Each copy of the DNA molecule, after replication, contains one strand from the original template and one newly synthesized strand.
Semiconservative
What is the difference betweeen Eukaryotic and Prokaryotic DNA
Pro- one origin of replication, circular DNA
Euk- multiple origins of replication, to replicate in a reasonable amount of time
What proteins bind to the single strands and prevent reannealing and protect DNA from nuclease degradation.
Single stranded binding proteins (SSBs)
What enzyme forms the replication fork by unwinding the DNA double helix?
DNA helicase
What enzyme removes the supercoiling by cutting one strand which allows the DNA to swivel around the intact strand, then seals the nicked strand.
Type I topoisomerase
What enzyme cuts both strands to relieve supercoiling, then re-ligates the two strands.
Type II topoisomerase
What enzyme is a type of Topoisomerase II that introduces (-) supercoils that are inhibited by quinolone drugs?
DNA gyrase
You can’t package DNA without this enzyme.
DNA gyrase
SInce DNA is antiparallel, the template must be read __ to __.
3’ to 5’
Nucleic acid synthesis is __ to __ and template reading is __ to __.
5’ to 3’
3’ to 5’
How is the other strand synthesized in DNA replication?
the other strand (the lagging strand) is synthesized discontinously… as replication fork advances, small fragments of DNA are synthesized 5’ to 3’ away from the replication fork
What are the discontinuously synthesized fragments called?
Okazaki fragments
_____ is an RNA polymerase that copies the first ~10 nucleotides to “prime” synthesis.
Primase
DNA polymerases require a free ______ group to begin synthesis. This problem is solved by the action of ______.
3’ OH
Primase
_________ is further cleaved to inorganic phosphate (Pi) to make the reaction irreversible, and drive the reaction in the forward direction.
Pyrophosphate
The enzyme in prokaryotes that elongates both the leading and lagging strands.
DNA polymerase III
3’ to 5’ exonuclease activity… Pol III checks each added nucleotide to make sure it is correctly base-paired with the template strand. This activity is called what?
Proofreading
What enzyme has has 5’ to 3’ and 3’ to 5’ exonuclease activity and removes RNA primer with dNTPS. (rNTPs with dNTPs)
Pol I
What enzyme seals the nick that remains after the RNA primer is removed and replaced with dNTPs?
DNA ligase
DNA replication steps»> what are they briefly?
Strand seperation (DnaA protein)
Prevent reannealing (SSB proteins)
Unwinding of DNA (Helicase)
RElieves supercoiling (Topoisomerase)
Leading and Lagging strands synthesized
RNA primer laid down to begin new strand (Primase)
Extension of leading and lagging strand (Pol III)
Removal of RNA primers and replaced with DNA (Pol I)
Nick sealed in the fragments (DNA ligase)
Leading strand synthesized __________, lagging strand synthesized _________.
Continuously
Discontinuously
_________ contains primase + DNA polymerase (begins strand synthesis)
Pol æ (Alpha)
_________is a Dna polymerase + proofreading (extends strands)
Pol D (Delta)
What adds nucleotides to extend the 3’ end of the DNA to help line up the strands.
Telomerase
What is an aspect of aging of a cell? What protects DNA on the ends?
Telomeres
Certain polymerases can copy RNA into DNA… What are 3 things that have this reverse transcription?
Reverse Transcriptase
RNA-dependent DNA polymerase
Telomerase
_____________ is a common strategy in many viruses like HIV because it lacks proofreading activity and there is high mutation rate.
Reverse transcriptase
A defect in mismatch repair is responsible for _____________________, one of the most common inherited cancers.
Hereditary nonpolyposis colorectal cancer (HNPCC)
Mutations can be caused by what other 4 things other than replication errors?
Spontaneous mutations
Exposure to chemicals
Radiation
UV light- (causes pyrimidine dimers instead of normal thymine dimers)
What enzyme does most of DNA repair?
Pol I in prokaryotes
What is a rare genetic disorder that results from a deficiency in excision endonuclease?
xeroderma pigmentosum
