DNA - Structure
Part A: Go to website: http://207.207.4.198/pub/flash/24/24.html and select DNA Structure
* Use this site as often as you like. Pause and rewind as much as you need in order to understand the structure
of DNA.
Complete the interactive questions handout.
Part B: After you are done Part A: Read pgs 210 – 215 of your text.
i) Complete DNA structure handout – label the distance between nucleotides, how many nucleotides make one
complete revolution in the DNA helix, label the distance from one revolution to the next revolution in a DNA
molecule.
ii) Answer # 1-10 in your text. *Skip anything you have answered during the interactive
Interactive Questions
1. Describe the structure of the DNA molecule (shape, subunits, number of strands).
2. Draw a nucleotide and label its three subunits.
3. Look at the purines and pyrimadines. Draw each nitrogenous base and classify them as being either a purine or
pyrimadine. What is the general difference between a purine and pyrimidine?
4. Draw a 3 nucleotide single stranded chain and label the phosphodiester bonds. Define phosphodiester bond.
5. DNA is a double stranded molecule. What force holds the two strands together? Between what nucleotide subunits
do these forces form?
6. For each complementary pair [A and T and C and G], draw the nitrogenous bases and with dotted lines draw the force
holding them together and label it.
7. Looking at your drawings, why do you think that A`s and C`s/G`s do not bond? Or Why don't T`s pair with C`s/Gs?
6. Distinguish between intrastrand bond and interstrand bondà. Name the intrastrand bonds and name the interstrand
bonds.
7. Define complementary. Which base pairs complement which other base pairs?
8. Draw the deoxyribose sugar molecule and label the carbons.
9. Draw a double stranded molecule of DNA, of course make your molecule so that it is unwound and you only have a
length of 3 nucleotides. Describe and label how a DNA molecule is antiparallel.
Structure of DNA