DNA Replication Flashcards
dna replication is?
semiconservative.
for eukaryotes, dna replication occurs during?
the s phase of the cell cycle.
organization of the genome: pro vs euk chromosomes?
prokaryotes have one circular chromosome.
eukaryotes have several linear chromosomes.
where does replication begin?
replication begins at specific sites along the dna called ORIGIN OF REPLICATION.
what direction does replication occur?
bidirectionally.
pro vs euk origin of replication?
prokaryotes: one origin of replication.
eukaryotes: multiple origins of replication.
proteins that recognize the ori…?
bind to the dna and start to unwind it forming a replication bubble.
what is at the end of each replication bubble?
the replication fork.
what is a helicase?
helicase protein binds at the replication fork unwinding the dna strands. the helicase moves down the dna as replication continues.
single stranded dna binding proteins?
these proteins bind to the single stranded dna and keep the strands separated.
topoisomerases?
bind to the dna and helps to relieve the torsional stress.
what does the dna polymerase do?
catalyze dna synthesis.
dna polymerase iii?
primary enzyme of replication at the replication fork in e.coli.
all dna polymerases synthesize dna in which direction?
5’ to 3’ direction.
what does dna polymerase require?
a free 3’ OH group.
how does dna polymerase make/elongate a new strand?
dna polymerase catalyzes the formation of a phosphodiester bond between the 3’ OH group of the growing chain and the first phosphate of the incoming nucleotide.
dna polymerases uses what as a substrate?
deoxynucloetide triphosphate: dNTPS
3 things are needed in order for dna polymerase to synthesize a complementary strand of dna?
- a template that will direct the synthesis of a complementary strand of dna
- a primer to provide a free 3’ OH group to which nucleotides can be added on to.
- dNTPS
dna polymerase needs something to add nucleotides on to?
makes use of the primer.
what is the primer?
the primer is a short piece of rna that is made by an enzyme called the primase.
what is the leading strand?
as chains are elongating, one is being replicated in a continuous manner. ONE PRIMING EVENT.
what is the lagging strand?
the chain that is being replicated in a discontinuous manner is called the lagging strand. MULTIPLE PRIMING EVENTS.
the segments of DNA that make up the lagging strand are called?
okazaki fragments.
what about the rna primer in the lagging strand?
it is removed by a different dna polymerase: dna polymerase i. it replaces them with deoxynucleotides.
what about the gaps between the okazaki fragments?
the gaps are sealed by an enzyme called dna ligase. the result is one continuous piece of dna.
