Biochemistry

DNA Structure Questions

Both HL & SL: Read the original article by Watson and Crick from Nature Journal. Then respond to the following on the back, or on a separate piece of paper.

1) Diagram a possible structure for DNA as proposed by Linus Pauling.

2) Draw an annotated diagram for Watson & Crick’s model of DNA – use the following terms in your diagram:

-All terms on 3.3 Vocab Sheet

-HL Only: Add purines and pyrimidines

3) Evaluate the significance of the following statement in Watson and Crick’s paper below. How might this relate to copying your DNA?

“It has been found experimentally that the ratio of the amounts of adenine to thymine, and the ratio of guanine to cytosine, are always close to unity for deoxyribose nucleic acid.”

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3) What two types of chemical bonds make up DNA? Compare the relative strengths of each bond.

HL Only: Read Section 7.1 in your textbook and answer the following questions:

5) There is approximately 2-3 meters of DNA (46 strands of DNA) in a typical human cell. In order for nucleus to divide, the DNA must condense itself into supercoiled structures we call chromosomes. Draw an annotated diagram of a supercoiled section of DNA “beads on a string.” Use the following terms:

-Nucleosome

-Histone protein

-H-1 histone protein

6) DNA can be grouped into three general “types”:

-Single Copy Genes

-Highly Repetitive Sequences

-Structural DNA

Contrast these three types of DNA. What do you think is the role of each type?