Unit 7 Lesson 1 Mastery Assignment
Name ____________________________________________
DNA (Deoxyribonucleic Acid) Structure and Replication
Purpose: To determine the structure of a DNA molecule and to discover how DNA replicates.
Background Information:
DNA stands for deoxyribonucleic acid. DNA is the genetic material found in the nucleus of most
cells. The building blocks of DNA are nucleotides. There are four different nucleotides that make
up DNA. You will analyze and manipulate the nucleotides in this activity to discover the structure
of DNA.
Materials:
Paper models including 12 nucleotides: 2 Adenine (A), 4 Cytosine (C), 4 Guanine (G), 2 Thymine (T)
Procedure:
Part A: Setup
1. Color the nucleotides the following colors:
a. Adenine – pink/red
b. Cytosine – blue
c. Guanine – green
d. Thymine – yellow
2. Cut out the nucleotides.
Part B: Components of DNA
3. What is the full name of DNA?
______________________________________________________________
4. What are the building blocks of DNA? _________________________________________.
5. Where in most cells is the DNA found? _________________________________________.
6. Look at the 12 different nucleotides given to your group. What are the three parts in a
nucleotide?
________________________, ________________________, ________________________
7. What two parts are identical between all the pieces?
__________________________ AND ________________________
8. What is the ONE part of a nucleotide that is DIFFERENT among the nucleotides in your
group? (Hint: look at the shape).
___________________________________
9. List the letters for the four nitrogen bases: _________, _________, __________, _______
These letters stand for adenine, thymine, guanine and cytosine.
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Part B: Structure of DNA
10. Now your group will work together and arrange all 12 of your nucleotides together like a
puzzle until you find the best fit. Make sure all of the words are facing up (don’t turn your
nucleotides over so you can’t see the text anymore). Some words may be upside down
though.
Your completed model should look like a ladder. Besides being shaped like a ladder, a DNA
molecule is twisted. It looks like a spiral staircase. However, your paper model cannot show
this shape.
11. If DNA is “ladder-like,” which two molecules of a nucleotide form the sides or upright
portion of the ladder?
____________________________ & ____________________________
12. Which molecules form the rungs or center part of the ladder?
_____________________________________
13. What letters pair with one another?
_______ pairs with________
_______ pairs with _______
This kind of pairing is called complementary. The attraction between two nitrogen bases
is called base pairing.
14. Practice: If the following are the bases on the left side of a DNA molecule. List the bases
that would make up the right side of a DNA molecule.
T
A
G
G
C
_____
_____
_____
_____
_____
15. Look at the strands you classmates have created. Do they have the same order as you?
(Yes/No) ___________
This is what makes us all different is the order of the bases. We all have the same 4 nucleotides
in our DNA but the order they are in is different!!!
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