dna model laura keller
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DNA ReplicationBy: Laura Keller
DNA
• The DNA double helix refers to the shape of the DNA molecule, or the twisted ladder. It has two intertwining strands made of sugar and phosphate with links across the middle. The rungs of the ladder are base pairs made of four different bases, represented by the letters A, T, G, and C.
The Enzyme DNA helicase “unzips” or unwinds the double stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands.
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= CytosineHydrogen Bond
3’
3’5’
5’
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= CytosineDN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
DN
A H
elic
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Then, on the leading strand, DNA Polymerase III adds the 5’ phosphate end of a free floating nucleotide to the exposed 3’ OH ends on the single stranded DNA in a continuous fashion. The leading strand elongates toward the replication fork.
Lead
ing
Str
and
Lagg
ing
Stran
d
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Then, on the leading strand, DNA Polymerase III adds the 5’ phosphate end of a free floating nucleotide to the exposed 3’ OH ends on the single stranded DNA in a continuous fashion. The leading strand elongates toward the replication fork.
Lead
ing
Str
and
Lagg
ing
Stran
d
DN
A P
oly
me
rase
III
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Then, on the leading strand, DNA Polymerase III adds the 5’ phosphate end of a free floating nucleotide to the exposed 3’ OH ends on the single stranded DNA in a continuous fashion. The leading strand elongates toward the replication fork.
Lead
ing
Str
and
Lagg
ing
Stran
d
DN
A P
oly
me
rase
III
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Then, on the leading strand, DNA Polymerase III adds the 5’ phosphate end of a free floating nucleotide to the exposed 3’ OH ends on the single stranded DNA in a continuous fashion. The leading strand elongates toward the replication fork.
Lead
ing
Str
and
Lagg
ing
Stran
d
DN
A P
oly
me
rase
III
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Then, on the leading strand, DNA Polymerase III adds the 5’ phosphate end of a free floating nucleotide to the exposed 3’ OH ends on the single stranded DNA in a continuous fashion. The leading strand elongates toward the replication fork.
Lead
ing
Str
and
Lagg
ing
Stran
d
DN
A P
oly
me
rase
III
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Then, on the leading strand, DNA Polymerase III adds the 5’ phosphate end of a free floating nucleotide to the exposed 3’ OH ends on the single stranded DNA in a continuous fashion. The leading strand elongates toward the replication fork.
Lead
ing
Str
and
Lagg
ing
Stran
d
DN
A P
oly
me
rase
III
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Then, on the leading strand, DNA Polymerase III adds the 5’ phosphate end of a free floating nucleotide to the exposed 3’ OH ends on the single stranded DNA in a continuous fashion. The leading strand elongates toward the replication fork.
Lead
ing
Str
and
Lagg
ing
Stran
d
DN
A P
oly
me
rase
III
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Then, on the leading strand, DNA Polymerase III adds the 5’ phosphate end of a free floating nucleotide to the exposed 3’ OH ends on the single stranded DNA in a continuous fashion. The leading strand elongates toward the replication fork.
Lead
ing
Str
and
Lagg
ing
Stran
d
DN
A P
oly
me
rase
III
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Then, on the leading strand, DNA Polymerase III adds the 5’ phosphate end of a free floating nucleotide to the exposed 3’ OH ends on the single stranded DNA in a continuous fashion. The leading strand elongates toward the replication fork.
Lead
ing
Str
and
Lagg
ing
Stran
d
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
`
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.D
NA
Pri
mas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
5’ 3’
3’ 5’
Lead
ing
Str
and
Lagg
ing
Stran
d
5’
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
3’ 5’
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DN
A P
rim
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
RNA Primer
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
RNA Primer
DN
A P
oly
me
rase
II
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
RNA Primer
DN
A P
oly
me
rase
II
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DNA
DN
A P
oly
me
rase
II
When the DNA
Polymerase II reaches the
RNA primer, it turns into
DNA.
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DNA
DN
A P
oly
me
rase
II
When the DNA
Polymerase II reaches the RNA primer, it turns into
DNA.
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DNA
DN
A P
oly
me
rase
II
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DNA
DN
A P
oly
me
rase
II
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DNA
DN
A P
oly
me
rase
II
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Then, on the lagging strand, which has to be built discontinuously, a short RNA primer is synthesized from DNA primase. The primer is extended in a 5’ to 3’ direction, with short DNA segments called Okazaki fragments formed from DNA Polymerase II.
DNA
Okazaki fragments
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
DN
A L
igas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
DN
A L
igas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
DN
A L
igas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
DN
A L
igas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
DN
A L
igas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
DN
A L
igas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragmentsD
NA
Lig
ase
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
DN
A L
igas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
5’
DN
A L
igas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
5’
DN
A L
igas
e
Key
= Phosphate
= Sugar
= Adenine
= Thymine
= Guanine
= Cytosine
Lead
ing
Str
and
Lagg
ing
Stran
d
Lastly, DNA Ligase forms a phophodiester bond to finalize the connection of Okazaki fragments.
DNA
Okazaki fragments
5’ 3’
3’
3’
3’ 5’
5’
5’
Why Does DNA Need to Replicate?
• DNA needs to replicate because when a cell in your body divides, in order for your body to grow or repair itself it must also duplicate the cell's DNA. This is so the cell will then have it's own set of directions to know how to continue replicating.
Where in Mitosis Does DNA Replication
Happen?• DNA replication happens in S Phase
and also in cytokinesis, or the last phase of mitosis.
Where in the Cell?
•DNA replication happens in the nucleus of a cell.
In My Own Words...
• Telomeres- keep chromosomes from becoming attached to each other accidentally.
• Okazaki Fragment- a section of complimentary strands of DNA formed when the enzyme DNA Ligase is present.
• DNA Ligase- an enzyme that “stitches” a new complimentary strand of DNA called an okazaki fragment.
• Telomerase- an enzyme that helps a cell maintain the length of their telomeres.
In My Own Words… (Continued)
• Cancer- expresses the enzyme telomerase, which helps a tumor to grow.
• Transplanted Cells- cells that have been taken, added to, and then given back
• Cloning- taking a piece of something and making another copy
• Aging- the steady shrinking of cells in the body
Mutations (Mistakes)
• If there are any mistakes while replicating DNA, it will result in the mutation of a gene. An organism can only have up to 3 mutations, or it cannot live. Sometimes, mutations are minor, while other times, they can change one’s whole genetic makeup. For example, a mutation can result in the crossing over of a 21st chromosome, resulting in one having Down’s Syndrome.
Works Cited• http://wiki.answers.com/Q/What_happens_if_there_
is_a_error_in_DNA_replication?#slide=6
• http://www.nature.com/scitable/topicpage/dna-replication-and-causes-of-mutation-409
• http://www.chemguide.co.uk/organicprops/aminoacids/dna6.html
• http://www.biology.ewu.edu/aHerr/Genetics/Bio310/Pages/ch13pges/ch13note.html
• http://www.astrochem.org/sci/Nucleobases.php
The End
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