DNA REPLICATION Flashcards
DNA strands serve as
template for synthesis of one another
two newly synthesized strands come together, original helix is preserved, this is what replication
Conservative
parental strands are dispersed into two new double helices, this is which replication
dispersive replication
in this replication, each replicated DNA molecule consists of one “old” and one new strand
Semiconservative
DNA replication in E.COLI is
semiconservative
what is the direction of DNA replication
bidirectional
what is the origin of replication of eukaryotic chromosomes
multipple origin of replication
bacterial chromosomes have how many origin of replication
single
when new DNA is synthesized in both direction from the single origin, it creates what
an expanding replication bubble
when is replication complete
when the replication fork meet
when an helix unwounds, it creates a
replication fork
length of DNA replicated is called
Replicon
requirement for replication in linear eukaryote
- template strand
- raw material: nucleotides
- enzymes and other protein
DNA synthesis / replication run from
5’ to 3’
DNA polymerase adds nucleotide to which end
3’ end of growing strand
what has the most characterized ORI sequences
yeast (Saccharomyces cerevusiae)
multiple origin of replication are called
Autonomously replicating sequences (ARS)
Initiation of replication process
- Dna A binds to the 9-mer repeats, bends DNA and breaks hydrogen bonds in the 13-mer regions
- DnaB is a helicase that uses ATP energy to break hydrogen bonds to separate the strand and unwind helix
- Dna B is carried to DNA helix by Dna C
- Unwound DNA are kept from reannealing by SSB
- unwinding of chromosomes leads to supercoiled DNA
- topoisomerases catalyze controlled cleavage and rejoins DNA to prevent overwinding
Can DNA polymerase initiate DNA strand synthesis on their own
no, they need RNA primers
what is teh name of the specialized RNA polymerase
primase
which DNA polymerase is abundant but not ideal for replication, its main job is clean-up
DNA polymerase I
which DNA polymerase is the principal replication polymerase
DNA polymerase III
WHICH DNA polymerase are involved in DNA repair
DNA polymerase II,IV & V
WHICH of these two strands does DNA polymerase synthesise 5’ to 3’ to 3’ to 5’
5’ to 3’
which is the continous DNA synthesis
leading strand
which is the discontinuous DNA synthesis
lagging strand
which polymerase is involved in removing an RNA primer nucleotide and adding a DNA nucleotide
DNA polymerase I
what happens when the primer removal is finished in the strand
dna ligase replaces pol I at DNA-DNA single strand gaps catalyzing formation of a phosphodiester bond
single steranded binding (SSB) protein coats single-stranded DNA to prevent
reannealing
why must DNA form a loop
so that both strands can replicate simultaneously
Characteristics of DNA replication
- Semiconservative
- bidirectional
- Semidiscontinous
when the leading strand copies continuously an dteh lagging strand copies in segments. This is called
semidiscontinuous
how is eukaryotic DNA replication differ from Bacterial Replication
multiple origin
Telomeres and telomerase
Ends of DNA contain a tandem repetitive sequence called
Telomeres
the answer to Teloneres is
telomerase
HOw do telomerase function
template RNA of telomerase allows new DNA replication to lengthen the telomere sequence
Once telomeres are elongated, polymerase synthesised additional RNA primers
New DNA replication then fills out chromosomes ends
telomerase is active in
germ-line cells and some stem sells in eukaryote
