Molecular
Genetics
,7 Genome Replication
λ
DNA- > RNA =
Polypeptide
?
↓ Genome info
all
genetic
:
↳
Transcripsome all Ra transcripts from Metabolome all metabolites
genome
: :
↳
Proteome : all expressed proteins
DnA Replication 弦
频道
ㄶ Semiconservative:
parentpnn strand produces daughter strand
ㄴ Topological problem
each a
: how to unwind DnA?
↓ y
↓ *
semiconservative conservative dispersive replication
·
, or mechanisms
Meselson -
Stall experiment
->
>
prove DNA is semiconservative
弦强
Afte replication composed of ni
·
1 : allDna was
·
Afte 2 replication : half was only light n , other half was intermediate
Topology of DnA how DNA strands intertwined
-
- are
↓
。亞.
negaziv supervoil: underwound DnA Clooser)
↓
positive supercoil overwound : DnA (tighter)
Topoisomerase cut and paste Dna to chance topological state
&>
Type 1 :
single-strand break
↳ 11 : double-strand
Type break
Gyrase introduces negative supercoils
·
that prevents over wounding
during Dna replication
:
Initiation of replication
↳ ORI
(origin of replication) : Where DnA strands are separated ,
forming a replication bubble with 2 bidirectional
replicatio forks
·
multiple ORI's in eukaryotes
Replicon =
parts of
genome that is replicated by a
Single ORI
, In E
. Coli initiation is
regulated by methylation of ORIC
↳ adenines (A) in the strands. If both strands active
Dam
methylase enzyme methylates are
methylated . Oric is -> start
↳ (one strand
Hemimethylated origins is methylated -
> inactive ,
no replication
When Oric isactive :
than wraps around and
7 .
DNAA (initiator protein) isactivated by ATP. First binds to
high affinity DnA , binds to
low affinity sites (AT rich) . HU helps twisting the helix .
>DNAB
- -
> DNAC
. TWO DNAB/DnAC
2 complexes unwind DnA (in 5'-3' direction) and forms 2
replication forkes. DNAB -
> helicase
3
.
Gyrase relaxes positive supercoils
. SSB
4 /single degradation
strand binding proteins) stabilize DNA -
keeps bubble open & protects against
-
>
other proteins bind as well ,
creating replication machinery
DNA polymerases
:
Dna Synthesis in 5'-3' ,
need a primer with Free On-end , have proofreading error system
(exunuclease activityin 3'-5 direction)
↳
Prokaryotes : Dnn
polymerase (1-V) . DnA
polymerase 1 :
DnA
Synthesis & enonuclease activity in both
directions. 11 -
>
repair, III =>
main
polymerase, Iv
-
>
repair & U => SOS response repair
↓ 1 &
Eukaryotes DNA Polymerase (0 B , Y primase elongation 2 repair,
-
:
,
... .
> - ,
-
0
SPPP TOM3
OM
↑ 8 & leading strand
; "
mitochondoia strand - >
? DnA, =
lagging ……
-
op
;.Tou
無 "
Semi-discontinuous replication :
leading strand is continuous (5'-3') lagging not (3-5')
,
Lagging
□
strand produced in small Okazaki fragments
-
> formed by RNA primers Eukaryotes pol : .
& is also primase
↳ Primase (DNA dependent
makes RNA primers RNA polmerase) ~ 10 nucleotides Prokaryotes needs primase
: & PD II
.
degraded gaps
·
filled sticked
RNA primers are , are
by put polymerase & Okazaki
fragments are
by ligase
E Coli
joining of Okazaki fragments in .
:
↳ DNA
pol. III
only has 3'-5' exonuclease
activity :
stops synthesizing when it finds another primer
↳
DnA pol .
I has both direction (3-5'0 5'-3') activity degrades primer : (5-3) and synthesizes new DNA
↳ DNA
ligase ligates the
fragments
, Joining in Eukaryates :
.
7 DnA polymerase 8 + helicase 'push' primer off ,
creating a 5'flap . DNA pol .
fills gap
. Flap endonuclease (FERI) cleaves of
2 the 5'flap -
> removes primer. Dna ligase ligates fragments
Elongatio of DnA replication
Progression of replication by gyrase , helicase, SSB , primase ,
Dna
polymerase III C 1 and ligase
Replisome links both DnA pol. .
together same
synthesizing rate at both strands :
Loop in
lagging strand allows DnA synthesis
↳2 DnA pol 2
dimerizing units 2
sliding clamps a clamp loader in th same direction of repl Fork
-
>
., , .
고 G
keeps DNA pol togethe
. assures contact between DNA & DNA POI. weeps structure
together
0
msinms
'
傅
"
@
gingaame
nm "
in
n
DnA polymerase
…
Termination
Replicatio forks meet halfway in the replication fork trap : 5 Ter sites are recognized by Tus =
replication forks stops
In eukaryotes : when2 bubbles meet , replication stops
The end problem
Lagging strand becomes shorter ,
lastR na primer cannot be replaced by DnA (no free On) -
>
shortening of chromosomes
Telomeres repeated sequences
: at end of chromosomes rich in a's . ,
↳ can be extended by telomerase to avoid shortening shelterin catalyzes Tloop formation,
↓ DNA repair and
Forms +
loop structure :
stabilizes end chromosome
of
protects telomeres from
↓ ends (no telomeres)
Enables cell so
recognize damaged degradation &
regulates length
Telomerase- reverse transcriptase (Dnn from RNA) , uses 3' end of G-rich strand as primer to elongate
↳
mainly active in dividing cells
3' end and
·
Attaches to uses ownRun as a template to built new DNA
polymerase completes opposite strand
·
Regular Dna
Genetics
,7 Genome Replication
λ
DNA- > RNA =
Polypeptide
?
↓ Genome info
all
genetic
:
↳
Transcripsome all Ra transcripts from Metabolome all metabolites
genome
: :
↳
Proteome : all expressed proteins
DnA Replication 弦
频道
ㄶ Semiconservative:
parentpnn strand produces daughter strand
ㄴ Topological problem
each a
: how to unwind DnA?
↓ y
↓ *
semiconservative conservative dispersive replication
·
, or mechanisms
Meselson -
Stall experiment
->
>
prove DNA is semiconservative
弦强
Afte replication composed of ni
·
1 : allDna was
·
Afte 2 replication : half was only light n , other half was intermediate
Topology of DnA how DNA strands intertwined
-
- are
↓
。亞.
negaziv supervoil: underwound DnA Clooser)
↓
positive supercoil overwound : DnA (tighter)
Topoisomerase cut and paste Dna to chance topological state
&>
Type 1 :
single-strand break
↳ 11 : double-strand
Type break
Gyrase introduces negative supercoils
·
that prevents over wounding
during Dna replication
:
Initiation of replication
↳ ORI
(origin of replication) : Where DnA strands are separated ,
forming a replication bubble with 2 bidirectional
replicatio forks
·
multiple ORI's in eukaryotes
Replicon =
parts of
genome that is replicated by a
Single ORI
, In E
. Coli initiation is
regulated by methylation of ORIC
↳ adenines (A) in the strands. If both strands active
Dam
methylase enzyme methylates are
methylated . Oric is -> start
↳ (one strand
Hemimethylated origins is methylated -
> inactive ,
no replication
When Oric isactive :
than wraps around and
7 .
DNAA (initiator protein) isactivated by ATP. First binds to
high affinity DnA , binds to
low affinity sites (AT rich) . HU helps twisting the helix .
>DNAB
- -
> DNAC
. TWO DNAB/DnAC
2 complexes unwind DnA (in 5'-3' direction) and forms 2
replication forkes. DNAB -
> helicase
3
.
Gyrase relaxes positive supercoils
. SSB
4 /single degradation
strand binding proteins) stabilize DNA -
keeps bubble open & protects against
-
>
other proteins bind as well ,
creating replication machinery
DNA polymerases
:
Dna Synthesis in 5'-3' ,
need a primer with Free On-end , have proofreading error system
(exunuclease activityin 3'-5 direction)
↳
Prokaryotes : Dnn
polymerase (1-V) . DnA
polymerase 1 :
DnA
Synthesis & enonuclease activity in both
directions. 11 -
>
repair, III =>
main
polymerase, Iv
-
>
repair & U => SOS response repair
↓ 1 &
Eukaryotes DNA Polymerase (0 B , Y primase elongation 2 repair,
-
:
,
... .
> - ,
-
0
SPPP TOM3
OM
↑ 8 & leading strand
; "
mitochondoia strand - >
? DnA, =
lagging ……
-
op
;.Tou
無 "
Semi-discontinuous replication :
leading strand is continuous (5'-3') lagging not (3-5')
,
Lagging
□
strand produced in small Okazaki fragments
-
> formed by RNA primers Eukaryotes pol : .
& is also primase
↳ Primase (DNA dependent
makes RNA primers RNA polmerase) ~ 10 nucleotides Prokaryotes needs primase
: & PD II
.
degraded gaps
·
filled sticked
RNA primers are , are
by put polymerase & Okazaki
fragments are
by ligase
E Coli
joining of Okazaki fragments in .
:
↳ DNA
pol. III
only has 3'-5' exonuclease
activity :
stops synthesizing when it finds another primer
↳
DnA pol .
I has both direction (3-5'0 5'-3') activity degrades primer : (5-3) and synthesizes new DNA
↳ DNA
ligase ligates the
fragments
, Joining in Eukaryates :
.
7 DnA polymerase 8 + helicase 'push' primer off ,
creating a 5'flap . DNA pol .
fills gap
. Flap endonuclease (FERI) cleaves of
2 the 5'flap -
> removes primer. Dna ligase ligates fragments
Elongatio of DnA replication
Progression of replication by gyrase , helicase, SSB , primase ,
Dna
polymerase III C 1 and ligase
Replisome links both DnA pol. .
together same
synthesizing rate at both strands :
Loop in
lagging strand allows DnA synthesis
↳2 DnA pol 2
dimerizing units 2
sliding clamps a clamp loader in th same direction of repl Fork
-
>
., , .
고 G
keeps DNA pol togethe
. assures contact between DNA & DNA POI. weeps structure
together
0
msinms
'
傅
"
@
gingaame
nm "
in
n
DnA polymerase
…
Termination
Replicatio forks meet halfway in the replication fork trap : 5 Ter sites are recognized by Tus =
replication forks stops
In eukaryotes : when2 bubbles meet , replication stops
The end problem
Lagging strand becomes shorter ,
lastR na primer cannot be replaced by DnA (no free On) -
>
shortening of chromosomes
Telomeres repeated sequences
: at end of chromosomes rich in a's . ,
↳ can be extended by telomerase to avoid shortening shelterin catalyzes Tloop formation,
↓ DNA repair and
Forms +
loop structure :
stabilizes end chromosome
of
protects telomeres from
↓ ends (no telomeres)
Enables cell so
recognize damaged degradation &
regulates length
Telomerase- reverse transcriptase (Dnn from RNA) , uses 3' end of G-rich strand as primer to elongate
↳
mainly active in dividing cells
3' end and
·
Attaches to uses ownRun as a template to built new DNA
polymerase completes opposite strand
·
Regular Dna
