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Chapter 10 Section 2 Reading Guide (p. 196-199)
Define the following words (USE THE GLOSSARY):
Nucleotide –
Deoxyribose –
Nitrogenous Base –
Purine –
Pyrimidine –
Base-Pairing Rules –
Complementary Base Pair –
Base Sequence –
1. Name the two scientists credited with discovering the structure of DNA.
2. They proposed that DNA is made of ________ chains that wrap around each other in the
shape of a _____________ _________________.
3. DNA is a _______________ __________________ made of two long chains of repeating
subunits called ______________________.
4. List the three parts of a nucleotide.
5. Draw and label a picture of a nucleotide (p. 197 bottom)
6. Name the 5-carbon sugar in DNA.
7. The “backbone” of the DNA molecule is made up of two alternating components that form
the “handrails” of the staircase, what are they?
8. _________________ bonds hold the bases of DNA together and join one strand to the other.
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9. List the four full names (and letters) of the bases in DNA. (p. 198)
10. These bases are of two different types of molecules: purines and pyrimidines. Purines have
_______________________ ring(s) in their structure, and pyrimidines have
_______________________ ring(s) in their structure.
11. Draw and label pictures of the four bases. (Fig. 10-7 p. 198)
12. The two bases that are purines are _____________________ and ___________________ while
the two bases that are pyrimidines are ________________________ ______________________.
13. Chargaff’s rule states that the DNA of any species contains equal amounts of
_______________________ and_______________________ and also equal amounts of
_______________________ and _______________________.
14. Based on this information, scientist could predict that the base _______________________
pairs with_______________________ and the base _______________________ pairs with
_______________________ in the formation of the DNA molecule.
15. The bases are paired by _______________________ bonds along the axis of the molecule.
16. Write the complementary sequence to following DNA strand:
Use the image at the right to complete the following:
17. Circle and label one nucleotide.
18. Label all of the sugars and phosphates.
19. Label the bases that are not already labeled
20. Color the DNA structure according to the key below.
Adenine = Red
Thymine = Blue
Guanine = Green
Cytosine = Yellow
Deoxyribose (5-Carbon Sugar) = Orange

DNA Structure Worksheet