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STRUCTURE OF DNA
Study Guide
KEY CONCEPT
DNA structure is the same in all organisms.
VOCABULARY
nucleotide
base pairing rules
double helix
MAIN IDEA: DNA is composed of four
types of nucleotides.
In the space below, draw a nucleotide and label its three parts using words and arrows
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1. How many types of nucleotides
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are present in DNA?
4
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2.
Which parts are the same in all nucleotides? Which part is different?
The phosphate group and the deoxyribose sugar; the nitrogen-containing base is different
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IDEA: Watson and Crick developed an accurate model of DNA,s
three-dimensional structure.
MAIN
3.
What did Franklin's data reveal about the structure of DNA?
that is was of uniform width
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4.
How did Watson and Crick determine the three-dimensional shape of DNA?
by building models
Unit 3 Besource Book
McDougal Linell Biology
Study Guide 65
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STUDY GUIDE, CONTINUED
5.
How does DNA base pairing result in
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a molecule that has a
uniform width?
The sugar-phosphate backbone is on the outside. Inside the structure, a base with two rings always pairs with a base
with only one ring.
MAIN IDEA: Nucleotides always pair in the same
6. What nucleotide pairs with T? with C?
T pairs with A
way.
G pairs with C
ln the space below, draw a DNA double helix. Label the sugar-phosphate backbone, the
nitrogen-containing bases, and the hydrogen bonds,
Vocabulary Gheck
7. Explain how the DNA double helix is similar to
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a spiral staircase,
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The sugar-phosphate backbone is like the twisting handrails of the staircase, and the nitrogen-containing
bases are like the steps that connect the railings to each other.
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How do the base pairing rules relate to Chargaff's rules?
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Because A only pairs with T and C only pairs with G, the amount of A will be equal to the amount of T,
and the amount of C will be equal to the amount of G.
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66
Study Guide
Unit 3 Resource Book
McDougal Littell Biology