Name: ______________________________________________
Biology – Period: ________
Date: _________________
Ms. Pozzuto
Activity 1: DNA Replication Notes
Every cell in your body must have an EXACT copy of all 3 BILLION of your DNA Base
Pairs…How does it make all of those copies?!
Steps to Replicate DNA:
Step
#1
Description
Picture
A ________________ molecule of DNA
Start with a parent molecule
is the original to be
of DNA
_________________.
An enzyme called ______________
comes in to _____________ and
#2
Unzipping the DNA strands
separate the _____ strands of the
parent DNA. It is called “helicase”
because it unzips the double
___________.
Each strand can be used as a
________________ to make a new
strand. If the single strand has an
#3
Adding the complementary
adenine, it would pair with a
________________, and if it has a
guanine, it would pair with a
base pairs
_________________. The enzyme
that joins the new bases is
called________________________.
Remember poly=___________.
DNA _________________ checks
and fixes any ____________ it
#4
finds. We now have 2
Proofreading (DNA Spell
_________________ strands. Each
Check)
_______________ to the parent
strand but with one _______strand
and one ______ each.
Candy DNA Replication
Introduction
Now that you have an understanding of the structure of the DNA molecule and the base
pairing rules, you are going to investigate DNA replication. Each time a cell divides it
makes an exact copy of itself. The process that DNA makes an exact copy of itself is
called DNA replication. During DNA replication the double helix is unwound by the
enzyme helicase and complementary nucleotides are attached to each of the 2 original
strands of DNA by the enzyme DNA polymerase.
Materials
4 Toothpicks
2 pieces of red licorice
4 yellow gummy bears
=
4 orange gummy bears = Thymine
4 green gummy bears = Cytosine
4 pink/red gummy bears =
Guanine
Adenine
Directions
1. Use your two red pieces of licorice to assemble a strand of DNA with the
following nucleotide sequence A-T-C-G. You will use the toothpicks to attach the
nitrogen bases (gummy bears) to the sugar-phosphate backbones (licorice).
2. Attach the complementary nucleotides to the other side of the toothpick (if you
have an A, attach a T, or G with C) and then attach the other red licorice piece to
this side of the strand.
3. Carefully color code and label your original strand of candy DNA in the space
provided, using all the labels listed in the directions on the observations table.
4. Using the scissors, separate the two strands by cutting down the middle (think
about what the action of the cutting scissors represents in DNA replication). This
portion of the lab will most likely not be done, BUT with your partner I want you
to think about if we did complete this portion what the NEW DNA strands would
look like and what the scissors represent.
5. You and your partner will both take one of the single strands from the original
molecule and add the NEW complementary base pairs.
6. Once the new base pairs are added you will close the molecule by attaching the
new backbone (black licorice).
7. Lay these two new strands next to one another so that both pieces of black
licorice are in the middle and both pieces of red licorice are on the outside.
8. Carefully color code and label your new strands of candy DNA in the space
provided, using all the labels listed in the directions on the observations table.
9. Complete the analysis questions.
Observations
Your diagrams should include the following labels and colors: Original Strand (RED),
New Strand (BLACK), Adenine (YELLOW), Guanine (PINK), Thymine (ORANGE),
Cytosine (GREEN)
Parent DNA strand
Daughter DNA strands
Analysis Questions:
1. How are your original and new strands SIMILAR?
2. How are your original and new strands DIFFERENT?
3. What did the following parts of your DNA model represent:
DNA
Replication
Represented by in your model…
EX: Adenine
The yellow marshmallows
Guanine
Cytosine
Thymine
Red licorice
Toothpicks
Helicase
DNA
polymerase
4. Why is it necessary for DNA replication to occur?
5. What kind of mistakes could happen in DNA replication (be specific)? How do you
think this could affect an organism?
Homework: Replication Reading
________________Biology I
Name: _____________________________________
Period: ___________