What does DNA stand for?
DNA Replication
D = deoxyribo + N = nucleic + A = acid
Put it all together and it spells-
deoxyribonucleic acid
When does DNA Replication occur?
What is DNA Replication?
Before Mitosis begins- Interphase
• Process by whicha cell makes a
copy of the DNA
in its nucleus.
Cell Division: Stage1- Interphase
History of DNA’s Discovery
Why is DNA Replication an important
cell process?
• Ensures that each daughter cell will
have all of the genetic information it
needs to carry out its activities.
Forming
daughter cell
DNA (genetic
information)
Forming
daughter cell
DNA (genetic
information)
* 1950’s scientists showed
DNA carries all cell’s
instructions.
* Learned DNA passed from
parent cell to its daughter
cells.
* 1953 James Watson and
Francis Crick discovered
structure of DNA by using
Rosalind Franklin’s lab notes
and pictures.
- Revealed important
information about how
DNA copies (replicates)
itself.
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Structure of DNA
Appearance of DNA
Phosphate
Sides (DNA Ladder)
• Alternating molecules of
Deoxyribose
sugar
• Deoxyribose sugar
• Phosphate
• Looks like spiral staircase
or twisted ladder
Rungs (DNA Ladder)
• Made up of pairs of
nitrogen bases
•Often called “double helix”
helixshape that twists
like threads of a
screw
• adenine
• thymine
• cytosine
• guanine
Ladder Rungs
Nitrogen
base
Pairing pattern of the nitrogen bases
• key to understanding how DNA
replication occurs.
•Letters A, T, G, C
•Used to represent the four
bases that make up
ladder’s rungs
•Nitrogen bases on one
side of ladder “match
up” in specific way with
bases on the other side.
•Adenine always pairs with
Thymine (A-T)
•Guanine always pairs
with Cytosine (G-C)
Nitrogen
Base
Replication Process
Step 1:
•Two sides of
the DNA
molecule
unwind and
separate
between paired
nitrogen bases
on each rung.
Nitrogen
base
Replication Process
Step 2:
•Nitrogen bases floating
in nucleus pair up with
bases on each half of the
DNA molecule.
•A always pairs with T
•G always pairs with C
•Like a zipper
unzipping
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Replication Process
Step 3:
•Once new bases are
attached, two new
DNA molecules
formed.
•Order of bases in
each new DNA
molecule exactly
matches the order in
the original molecule.
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