Name __________________________________________________________ Date ____________ Period _______
Building DNA Nucleotides : DNA Class Model
DNA (deoxyribonucleic acid) is a nucleic acid -a
macromolecule that stores hereditary information. It
consists of individual units called nucleotides, which
have three components: a sugar, a phosphate group,
and a nitrogen containing molecule called a base.
Adenine and Guanine
Phosphate Group
Nitrogenous Base
Deoxyribose (sugar)
5’
The physical structure of DNA is frequently described as a “double helix,” and can be imagined as
a twisted ladder. The sugar in DNA is always
deoxyribose and the phosphate group is always the
3’
same. The alternating sugar-phosphate ‘backbone’
provides structure for the molecule.
Cytosine and Thymine
Attached to each sugar, and protruding inward like
Popsicle sticks (2 inches showing)
half of a rung on the ladder, is one of the four
5’
nitrogen-containing bases. The four bases are
adenine, thymine, cytosine and guanine.
During DNA synthesis (making copies of DNA)
additional nucleotides are added to the 3’ end of the
3’
previous nucleotide (read 3 prime). The 3’ and 5’ ends
are essential to DNA synthesis and can be visualized on the
nucleotides to the right.
Both backbones of the DNA ladder have a base protruding
from each deoxyribose sugar. In a double helix, the base on
one side of the ladder forms weak hydrogen bonds with a base
on the other strand, and together they are called a base pair.
The base Adenine only bonds with the base Thiamine while
Guanine only bonds with cytosine (Chargaff’s Rule). Using
Chargaff’s rule, given the DNA sequence of one strand, you
can always find the sequence of the complementary strand.
For example, if one strand reads ATCG, the complementary
strand must be TAGC.
Materials
☐ Scissors
☐ Instruction Handout
☐ Popsicle sticks (covalent bonds)
☐ Glue-stick
☐ Nucleotide Cut-outs Handout
☐ Cardboard
☐ Elmer’s Glue
☐ Colored pencils (green, yellow, red)
Procedure
☐ Label each nucleotide component correctly with a sharpie: deoxyribose sugar, phosphate
group, your base (Adenine, Cytosine, Thymine, Guanine)
☐ Color the nucleotide components the following colors (sugar = red, phosphate = yellow and
base = green - see image above)
☐ Cut out the nucleotide components, glue down to cardboard using a glue stick, then cut out
again.
☐ Arrange the nucleotide components so they align exactly as you see in the image above (this
will be slightly different depending on your nitrogenous base – A, T, C or G).
☐ Using a hot-glue gun attach the components together via covalent bonds (Popsicle sticks).
☐ Once you’ve completed your individual DNA nucleotide, find a partner to form a base pair with
via hydrogen bonds (string). Try to attach so that the nucleotides are 20 cm apart.
☐ Once you have completed your base pair add this to your class model.
Name __________________________________________________________ Date ____________ Period _______
Analysis
1. Deoxyribonucleic acid (DNA) is made up of individual monomers (units)
called what?
2. Label the three components of a nucleotide to the right.
3. The DNA in every living thing is made of the same stuff,
nucleotides. You look vastly different than a banana; if the same
four nucleotides that make up your DNA are the nucleotides that make
up a banana why do you look so different? (Hint: There are only 26 letters in the alphabet)
4. LABEL and COLOR the DNA molecule to the left according to the following rules:
a. Color the deoxyribose sugars red
b. Color the phosphates yellow
c. Color the strong covalent bonds dark blue
d. Color the weak hydrogen bods green
e. Label the 3,’ and 5’ ends of both DNA stands