DNA REPLICATION Flashcards
double stranded molecule
DNA
A nucleotide is composed of PSN
Phosphate group
Sugar (Deoxyribose)
Nitrogenous base
Phosphorous atom bonded to 4 oxygen
Phosphate group
named as such because of the absence of oxygen atom at the 2 carbon
Sugar (Deoxyribose)
________ is directional, and this arises from the orientation of
the deoxyribose sugar
DNA
_____________forms the backbone of DNA
Sugar and phosphate
Refer to the 3’ and 5’ ends of the DNA
DNA BACKBONE
The base is connected to ________
1 carbon
The phosphate is connected to _________
5 carbon
The last trailing of the carbon is ______
3 - 5 ends of DNA
Nucleotides in the DNA backbone are bonded from phosphate to sugar between 3 and 5 carbons
ANTI PARALLEL STRANDS
Complementary strands run in ___________
opposite direction
One strand is ______ direction while the other strand is _________ direction
5 to 3 and 3 and 5
DNA molecule has ______
direction
Base pairing is present in the _________
DNA
The bases that occur in ________, ________, _______ and _______
Adenine
Guanine
Cytosine
Thymine
AGCT
The _________ unique to the DNA that doesn’t occur in RNA
nitrogenous base
Base pairing in DNA
Purines
Pyrimidines
Pairing
PPP
Purines
Adenine (A)
Guanine (G)
Pyrimidines
Thymine (T)
Cytosine (C)
Pairing
A:T - 2 hydrogen bond Adenine and Thymine
C-G - 3 hydrogen bond Cytosine and Guanine
ATCG
2 hydogen bonds
A and T
3 hydrogen bonds
C and G
________ are weak bonds
Hydrogen bonds
_________ is the process by which a double-stranded
DNA replication
____________is copied to produce two identical DNA
molecules
DNA molecule
Replication
copying
it produces 2 newly synthesized identical molecules DNA
DNA REPLICATION
There 3 several models about DNA replication:
- Semiconservative Replication
- Conservative Replication
- Dispersive Replication
○ DNA replication would create two molecules
○ each of them would be a complex of an old
(parental) and a daughter strand.
○ example: Red from old & Blue from brand new
- Semiconservative Replication
○ DNA replication process would create a brand new
DNA double helix made of two daughter strands
while the parental chains would stay together
- Conservative Replication
○ Replication process would create two DNA
double-chains, each of them with parts of both
parent and daughter molecules
○ The old DNA double helix is shattered or
separated into pieces and the parts will join the
newly synthesized DNA
○ the new strands contain a part of the old and
daughter molecule
- Dispersive Replication
__________ occurs during interphase of the cell cycle
Synthesis phases
this is where the cells are growing, and are
performing cellular tasks and replicating
SYNTHESIS PHASE
_________has to be copied before a cell divides
DNA
__________first then Cell Division
DNA replication
_________replicates about 50 bases per
second
Human DNA
__________ is copied during the S or synthesis phase of
interphase
DNA
___________ (bacteria) have a single bubble
Prokaryotes
DNA replication happens simultaneously at both strands (in _’ - _’ and _’ - _’)
5-3
3-5
Unwinds the DNA double helix
(unzipping enzyme)
HELICASE
_______ chromosomes have MANY bubbles
Eukaryotic
The correct model is the ____________
as was proven by the experimentation of Matthew Meselson
& Franklin Stahl
semiconservative DNA Replication
Synthesizes short
oligonucleotides ( primers)
(initializer)
Creates primer so that the DNA
polymerase can figure out
where to go and start replication
PRIMASE
Allows the leading strand to be
threaded through
CLAMP PROTEIN
Joins the assembled
nucleotides
Acts as a builder
DNA POLYMERASE
Joins Okazaki fragments in the
lagging strand
(Gluer)
Glues okazaki fragments
together
LIGASE
There are several DNA polymerase: _____, ____, _____
1 2 3
utilized in filling in small DNA
fragments during replication and repair when we add and
remove nucleotide one at
DNA Polymerase I:
an alternative repair polymerase
used to replicate DNa if the template is damaged
DNA Polymerase II:
major DNA polymerase used to
normal replication (primary polymerase)
DNA Polymerase II
___________ is synthesized continuously as a single
strand from the point of origin toward the opening replication fork
The Leading Strand
series of short segments on the lagging
strand
Okazaki Fragments
– keep the strands separated after the helicase
has separated the 2 strands since there is a possibility
that they will join again
Single-Stranded Binding Proteins
attach and keep the 2
DNA strands separated and untwisted
Single-Stranded Binding Proteins (SSBs)
link the bases of two DNA
strands
Hydrogen bonds
the site where the DNA is locally
opened resembling a fork
Replication fork
attracts complementary RNA nucleotides a
short piece of RNA called RNA primer
▪ synthesizes the prime
Primase
built at the start of each segment of DNA to
be replicated
▪ attracts DNAP (DNA Polymerase) to decide
where it will add the DNA nucleotides
▪ before the new DNA strands could be formed
RNA primer
▪ add new complementary bases
▪ DNA polymerase III
▪ If the base is cytosine, then in the new or
complementary strand it should be guanine.
▪ If the base is thymine, then in the new strand
the base should be adenine
Build daughter DNA strand
Continuous synthesis
Leading Strand
Okazaki fragments
Joined by ligase (aka “spot
welder” enzyme)
Lagging Strand
derived from a Latin word which means “to
tie”
▪ joins the Okazaki fragments and will later on
seal the other nicks in sugar phosphate
backbone
Ligase
will keep the two strands separated
SSB
unwinds the DNA
Helicase –
relax the tight supercoils
Topoisomerase
– creates the primer
Primase
will signal the start of base-pairing
Primer
will add bases once there is primer
DNA polymerase III
will join the fragments together
Ligase
