8b Flashcards
Define dna replication?
process by which DNA is duplicated, DNA—>DNA
Name the 3 possible mechanisms of dna replication
semiconstructive mechanism
conservative mechanism
dispersive mechanism
define semiconstructive mechanism
dna replication produces 1 with parental strand and 1 newly made strand.
define conservative mechanism
1 double helix with both parental strands and 1 with 2 new daughter strands
define dispersion mechanism
dna strands in which segments of new dna+parental dna are present 🧬
_______Showed that DNA Replication is semi-conservative.
Meselson and stahl experiment
what is the molecular process of semi conservative replication
1.untwisting of dna molecule-both the strands as templates
2.DNA polymerase help to link free nucleotides to form new strands.
3.new and old template antiparallel
untwisting of dna molecule?
Helicase, breaking the H bonds between nitrogenous bases
after dna is divided into 2, each of the
2 strands are called_________
template
what helps in the linking of nucleotide to form a new strand?
DNA polymerase
the nucleotides are always added at what end?
3’- end, has a free OH group
the nucleotides are connected to form the _______ of the new strands.
sugar-phosphate back bone
replication fork
very active area where dna replication takes place
topoisomerase?
avoid twisting of the DNA ahead of the replication fork by cutting the DNA, turning the DNA on side of the break in direction opposite to that of the twisting force and rejoining the twisting strand.
____________ stabilizes single stranded DNA and prevent the 2 strands at __________ from reforming ______.
single-stranded binding proteins
replication fork
double stranded DNA
function of primase?
assembles RNA primers in the 5’ to 3’ direction to initiate a new DNA strand
what is the function of sliding clamp?
attaches DNA polymerase III to the DNA template, making replication more efficient
which is the main replication enzyme in E. coli?
DNA polymerase III
function of DNA polymerase III
extends the RNA primer by adding DNA nucleotides to it, synthesize new DNA strands during replication
function of DNA polymerase I
removing RNA primers and replacing them with DNA nucleotides
what is responsible for synthesizing Okazaki fragments?
dna polymerase III
tell 4 uses of dna polymerase 1?
1.primer removing and gap filling
2.exonuclease activity from 5’to3’ and 3’to5’.
3.nick sealing (dna ligation)
define primer removing?
dna polymerase I removing the RNA primers and adding dna nucleotides, aka primer removal and gap filling
DNA ligase functions to seal nicks and gaps in the adjacent bases by catalyzing the formation of phosphodiester bonds after RNA primers replaced with dna. Its main roles include joining Okazaki fragments during DNA replication, repairing DNA damage, and facilitating recombination events.
what are Okazaki fragments
short, discontinuous DNA segments synthesized on the lagging strand , subsequently joined by DNA ligase to form a complete and continuous complementary strand.
__________ joins short, discontinuous DNA segments to form a continous complementary strand?
DNA ligase
________ have a single origin.
bacteria
what is the rate of replication in bacteria as well as eukaryotes?
bacteria:500-1000 nucleotides per second
eukaryotes:50-100 per second
