Name _______________________________________
Section 8.3: DNA Replication
Date __________________
Main Ideas:
 DNA is precisely copied in a method known as DNA Repliation
 The DNA replication needs protein enzymes to carry out the process
 DNA replication is accomplished extremely quickly and accurately
Vocabulary:
 Replication

DNA Polymerase
Remember when we did cell division/reproduction, and you learned about the phase in mitosis and meiosis
called Interphase? This section is how the DNA is copied precisely during the S (Synthesis) phase of
Interphase.
1. What did Watson and Crick mean by their statement “It has not escaped our notice that the specific
pairing (of nitrogen bases) … suggests a possible copying mechanism for the genetic material
(DNA)”?
2. Define replication.
3. What is needed to ensure that the new replicated DNA strand is identical to the original strand?
4. Discuss the function of the DNA polymerases in DNA replication.
5. Let’s go through the process of DNA Replication in 3 steps.
I.
Enzymes ______________________ the two strands of DNA at the ____________ bonds. This
exposes the _______________ of each strand. This unzipping occurs in ___________
directions.
II.
Free-floating ______________________ will bond one by one to the exposed bases. The
enzyme, DNA _________________________ will bind the new bases to the exposed ones.
III.
______ identical strands of DNA will now be produced. The outer strands are from the
_______________ DNA strand and the inner ones are the _____ strand.
6. DNA replication is VERY fast. How fast is it? ______ nucleotides added every _____ second. To
make it go faster, instead of it unzipping and rezipping like a jacket, there will be many ________ of
replication as shown in Figure 8.9.
7. DNA proof-reading is accurate to one error in every 1 _______________ nucleotides!! Can you do
that?
8. Below is a strand of DNA showing only the nitrogen bases. The first diagram is the original strand.
Show in steps what the two new strands will look like. Fill in the missing nitrogen bases.
Original DNA strand
DNA being replicated
New DNA Strands following replication
C–G
A–T
T–A
G–C
C–G
C–G
T–A
T–A
A–T
G–C
C–G
A–T
T–A
G–C
C–G
C G
T-__ __-A
T-__
__-A
A-__
__-T
G-__
__-C
C – __
A – __
T – __
G – __
C – __
C – __
T – __
T – __
A – __
G – __
__ – G
__ – T
__ – A
__ – C
__ – G
__ – G
__ – A
__ – A
__ – T
__ – C
9. After going through the process of DNA replication, what can you conclude about the two new DNA
strands formed?
10. Do you see the original strand on the outside of the two new strands?