DNA Replication Flashcards
What is replication?
duplication of DNA
When does DNA replication occur?
S phase in interphase of the cell cycle
What does it mean for DNA replication to be semiconservative?
new daughter strands are synthesized using the parental DNA as a template to copy from; each new daughter strand is perfectly complementary to the parental strand
What is the helicase?
enzyme that unwinds, separates and stabilizes double stranded DNA
What is the place that helicase begins to unwind the DNA?
ORI; origin of replication
What protein in bacteria will find the ORI?
DnaA
What are topoisomerases?
enzymes that cut one or both double strands and unwrap the helix, releasing the excess tension caused by the helicase
What are SSBPs?
single-strand binding proteins; protect the DNA that has been unpackaged and help keep the strands separated
What is the open complex?
when the two strands are separated
What must occur prior to replication of DNA?
RNA primer must be synthesized for each template strand
What enzyme/proteins is involved in creating the RNA primer?
protein complex = primosome
enzyme = primase
What catalyzes the elongation of the daughter strand?
DNA polymerase
What complex is DNA polymerase a part of?
replisome
What is the thermodynamic driving force for polymerization reaction?
removal and hydrolysis of pyrophosphate from each dNTP added to the chain
Which direction does polymerization occur?
5’ to 3’
What is the replication fork?
areas where parental double helix continues to unwind
What are leading strands?
strands that elongate continously into the widening replication forks
What are lagging strands?
must wait until the replication fork widens before beginning polymerization
What are Okazaki fragments?
small chunks of DNA comprising the lagging strand
What are the two important DNA polymerases found in prokaryotes?
DNA Poly III
DNA Poly I
What is the function of DNA poly III?
fast elongation of the leading strand; it has proofreading capabilities
What is the function of DNA poly I?
starts at nucleotides at the RNA primer; has poor processivity
What is the Hayflick limit?
number of times a normal human cell type can divide until telomere length stops cell division
What is telomerase?
enzyme that adds repetitive sequences to the ends of chromosomes and lengthens telomeres
What cells is telomerase expressed in?
germ line, embryonic stem cells, and white blood cells
What enzyme is responsible for connecting the Okazaki fragments together?
DNA ligase
What is exonuclease?
cutting a nucleic acid chain at the end
What is endonuclease?
cutting a nucleic acid chain in the middle
What are restriction enzymes?
endonucleases found in bacteria
