GENE EXPRESSION I Flashcards
cell division occur
parent cell will divide into two daughter cells
mitotic phase
responsible for variation in cell cycle in different organisms
cell’s irreversible decision to proliferate is made here
may enter a quiescent phase
G1 gap phase
only period where DNA is synthesized
DNA replication precedes between actual cell division during mitosis
synthetic phase
cells are prepared for mitosis
promoted by cyclin protein that triggers entry of cells into M phase
G2 phase
STEPS IN DNA REPLICATION
involves association of sequence-specific double stranded (dsDNA) binding protein to DNA
dsDNA binding protein attaches to 150-250 base pair DNA sequences adjacent to a region rich in adenine and thymine
identification of ori site
STEPS IN DNA REPLICATION
formation of protein to protein and protein to DNA interactions
unwinding DNA
STEPS IN DNA REPLICATION
__________- unwinds short segments of DNA
hydrolyzes ATP- endergonic process
helicase
STEPS IN DNA REPLICATION
helicase
protein to protein interaction
DNA B helicase
STEPS IN DNA REPLICATION
helicase
protein-DNA interaction
DNA C protein
undwinding of DNA
______________ cuts a single strand of the duplex
___________ nicks both strands
DNA topoisomerase I
DNA topoisomerase II
DNA toposiomerase twists the duplex in the direction which favors __________
unwinding
STEPS IN DNA REPLICATION
branch point in a replication eye at which DNA synthesis occur
formation of replication fork
replication fork sequence of 4 events
________ unwinds parental DNA
________initiates the synthesis of RNA primer
________ initiates synthesis of daughter strand
_________ binds to single strand DNA
helicase
primase
DNA polymerase
SSB
STEPS IN DNA REPLICATION
DNA polymerase is principal enzyme involved; elongates the daughter DNA from 5’ to 3’ direction
leading strand is replicated continuously
elongation step
DNA polymerase I has 3 enzymatic activities
___________ - gap filling
___________ - allows Pol I to edit its mistakes
___________- removes the RNA primer
polymerase
3-5 exonuclease
5-3 exonuclease`
participates in DNA repair
has 3’ exocnuclease activity only
DNA polymerase III
major DNA replicase has 10 subunit complex
core subunits consists of alpha, epsilon, and beta subunit accounts for high stability of the complex
DNA Polymerase III
EUKARYOTIC DNA POLYMERASES
replicates DNA by extending a primer in 5-3 direction
has a tightly associated primase activity
lacks exonuclease activity
DNA polymerase alpha
EUKARYOTIC DNA POLYMERASES
lacks primase activity
exhibits a proofreading 3 prime exonuclease activity
eukaryotic lagging strand synthesis
DNA polymerase delta
EUKARYOTIC DNA POLYMERASES
highly processive leading strand synthesis
function is facilitated by proliferating cell nuclear antigen
DNA polymerase epsilon
EUKARYOTIC DNA POLYMERASES
participates in DNA repair
DNA polymerase beta
STEPS IN REPLICATION
done by DNA polymerase I in prokaryotes and DNA polymerase delta in eukaryotes using their 5’ exonuclease acitivity
removes RNA primer nucleotide by nucleotide
removal of RNA primer
STEPS IN REPLICATION
done by DNA ligase which connects the okasaki fragments to the lagging strand of the growing daughter DNA
splicing the okazaki fragments
STEPS IN REPLICATION
done by the 3’ exonuclease activity of DNA polymerases in prokaryotes and eukaryotes reason for the high degree of fidelity of replication
proofreading and correction errors
