6 BIOC0005 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
who demonstrated semiconservative nature of DNA replication
Meselson and Stahl
Bacteria grown in 15N; all DNA is heavy
Transfer to 14N medium
Continued growth in 14N
produce hybrid
types of DNA
-B form, right handed, helix turn every 3.4 nm and distance b/w two bases is 0.34 nm,
10 bp per turn
most common
-A form due to hight salt concentration or alcohol added, right handed, 2.3 nm makes a
turn and 11 bp per turn.
-Z form, alcohol or high salt-concentration, making the DNA molecule alternating G-C
sequence. Left handed, 4.6 nm per turn and 12 bp.
Where to begin replication? - Prokaryotes
,• Origin of replication is called OriC in prokaryotes
• Only one origin of replication in prokaryotes, multiple origins of replication in
eukaryotes.
• DNA replicated from one origin of replication is called a replicon.
• Only one replicon in prokaryotes.
• Ter regions for termination of replication
Prokaryotes have a single origin of replication
Where to begin replication? - eukaryotes
A eukaryotic chromosome contains multiple origins of replication that ultimately merge
during replication.
Multiple replicons in eukaryotes on each chromosome
replicator and initiator regions defined by
(e.coli)
repeated sequences
9 mer, 5 repeated
13 mer, 3 repeated
9-mer region E.coli for
binding DnaA protein
tandam array of 13 mer seq rich in
AT
Roles of DnaA, DnaB and DnaC (E.coli)
, • DnaA binds to double stranded 9mer regions. Hexamer
• When DnaA is bound to ATP it can interact with DNA in 13mer region that results in it
separating to single
stranded DNA.
• DnaA recruits complex of DnaB/helicase and DnaC/helicase loader respectively.
• Helicase is inactive when bound by the helicase loader and only activated when
loaded onto DNA by helicase loader.
Replication scheme
DnaA hexamer + protein bind 9 mer sequence
DNA polymerase is recruited and replication can proceed
Primer provides 3' hydroxide group for DNA polymerase
One leading
Two on lagging. strand
Polymerisation of leading and lagging strands
Primer provides
3' hydroxide group for DNA polymerase
3 DNA Pol III holoenzymes are involved in replication
One on the leading strand and two on the lagging
strand.
DNA primase associates with DNA helicase and
synthesises a new primer on the lagging strand
trombone model
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
who demonstrated semiconservative nature of DNA replication
Meselson and Stahl
Bacteria grown in 15N; all DNA is heavy
Transfer to 14N medium
Continued growth in 14N
produce hybrid
types of DNA
-B form, right handed, helix turn every 3.4 nm and distance b/w two bases is 0.34 nm,
10 bp per turn
most common
-A form due to hight salt concentration or alcohol added, right handed, 2.3 nm makes a
turn and 11 bp per turn.
-Z form, alcohol or high salt-concentration, making the DNA molecule alternating G-C
sequence. Left handed, 4.6 nm per turn and 12 bp.
Where to begin replication? - Prokaryotes
,• Origin of replication is called OriC in prokaryotes
• Only one origin of replication in prokaryotes, multiple origins of replication in
eukaryotes.
• DNA replicated from one origin of replication is called a replicon.
• Only one replicon in prokaryotes.
• Ter regions for termination of replication
Prokaryotes have a single origin of replication
Where to begin replication? - eukaryotes
A eukaryotic chromosome contains multiple origins of replication that ultimately merge
during replication.
Multiple replicons in eukaryotes on each chromosome
replicator and initiator regions defined by
(e.coli)
repeated sequences
9 mer, 5 repeated
13 mer, 3 repeated
9-mer region E.coli for
binding DnaA protein
tandam array of 13 mer seq rich in
AT
Roles of DnaA, DnaB and DnaC (E.coli)
, • DnaA binds to double stranded 9mer regions. Hexamer
• When DnaA is bound to ATP it can interact with DNA in 13mer region that results in it
separating to single
stranded DNA.
• DnaA recruits complex of DnaB/helicase and DnaC/helicase loader respectively.
• Helicase is inactive when bound by the helicase loader and only activated when
loaded onto DNA by helicase loader.
Replication scheme
DnaA hexamer + protein bind 9 mer sequence
DNA polymerase is recruited and replication can proceed
Primer provides 3' hydroxide group for DNA polymerase
One leading
Two on lagging. strand
Polymerisation of leading and lagging strands
Primer provides
3' hydroxide group for DNA polymerase
3 DNA Pol III holoenzymes are involved in replication
One on the leading strand and two on the lagging
strand.
DNA primase associates with DNA helicase and
synthesises a new primer on the lagging strand
trombone model
