DNA Structure MODEL Lab

Prelab Assignment:

  1. Label the diagram below by writing the printed CAPITAL letter of the correct word from the list below.

SkillsApplicationsConcepts

  1. cell
  2. nucleus
  3. DNA
  4. hydrogen bonds
  5. nitrogen base
  6. sugar-phosphate backbone

SkillsApplicationsConcepts

  1. Label the nucleotides shown in the space below by coloring the molecules as follows:

SkillsApplicationsConcepts

  • deoxyribose (pentagon) – red
  • phosphate – purple
  • guanine – green
  • cytosine – yellow
  • thymine – orange
  • adenine – blue

SkillsApplicationsConcepts

  1. Read the background on the next page.

Background:

Part 1: Nucleotide Structure

DNA – deoxyribonucleic acid – one of two nucleic acids composed of nucleotide monomers that carries the genetic information from one generation to the next; found in double stranded helices in the nucleus of eukaryotic cells (cells with a nucleus)

Purpose:

The purpose of this lab is to investigate the structure of the nucleotides that make up DNA using an accurate model.

Materials:

colored pencils

DNA model kit

Tips:

  1. DNA is made of 4 different nucleotides:

- Carefully look at the set of pieces assigned to your group.

- Quickly identify the 6 different pieces by color: orange, red, blue, green, yellow and purple.

  • The key to this model is the red piece. The red piece is labeled below:

Procedure for assembling the 4 different nucleotides:

  1. From the kit, take out:
  2. 4 red sugars
  3. 4 purple phosphates
  4. 1 of each of the Nitrogen bases (A, T, G, C).
  5. Connect 1 red sugar to each Nitrogen base by using the STRAIGHT red peg on sugar and hole in corner of a Nitrogen base.
  6. Connect 1 purple phosphate to the BALLED peg.
  7. After assembling your 4 different nucleotides, answer the questions below.

Questions:

  1. What are the 3 parts of a nucleotide?

______, ______, ______.

  1. In the boxes below:
  1. Draw and COLOR each of the 4 different nucleotides built in this lab (a quick sketch is fine, the Nitrogen bases don’t have be drawn exactly how the piece looks).
  2. Label them by their name (Adenine, Thymine, Guanine, or Cytosine)
  3. Label each nucleotide as a purine or a pyrimidine.
  1. a. What do the pegs on the yellow, green, blue and orange pieces represent?

______bonds

b. How many pegs were between the blue and orange pieces? ______

How many were between the green and yellow pieces? ______

  1. Why is the red piece a pentagon? ______
  1. Which piece of the side chain attaches to the nitrogen base? phosphate OR sugar

(circle one)

Background:

Part 2: Deoxyribonucleic Acid Structure

Purpose:

The purpose of this lab is to investigate the structure of the DNA molecule using an accurate model showing that DNA is a double helix with antiparallel strands.

Materials:

colored pencils

DNA model kit

Procedure:

*****CAUTION: DO NOT FORCE ANY OF THE PIECES TOGETHER OR APART. THIS WILL DAMAGE THE MODEL!!!*****

  1. To begin the DNA model,have one or two group members complete the following, the other two group members should be doing procedure step 2 that begins at the top of the next page:
  2. Join the all of the orange and blue bases together, then join all of the green and yellow bases together.
  3. Next, screw together the two pieces of the pole and insert the pole into the base.
  4. Slide ONE of the base pairs onto the pole, then place a spacer. Then the next base pair, then another spacer. Continue until all bases are placed with a spacer between each.
  5. Turn each of the base pairs to that the holes at the corners are ALL facing the same direction.
  1. While one or two group members are completing #1 on the page before, the other two group members should do the following:
  2. Use the redsugars and purple phosphates to create two alternating chains of 11 red and 11 purple pieces in each chain. (DO NOT connect these to the bases yet)
  3. The hole of the purple piece (phosphate) should be connected to the angular peg with the ball on top on the red piece (sugar) so that purple piece is pointed down (see picture in the model kit info sheet next to 4.)
  4. Next, connect the hole of a red sugar to the peg of the purple phosphate so that you now have three pieces of your chain.
  5. Continue following steps b. and c. until you have a chain with 22 pieces total (11 red and 11 purple)
  6. Repeat steps a.- d. to make your second chain
  1. Take your chains and now connect them to the nitogen base pair “tower”.
  1. Starting at the bottom of the nitrogen base pair “tower”, connect the red peg that is left to the nitrogen base in the model, carefully turning the model as you go to avoid stressing the pegs and damaging the model. The “peaks” of the purple pyramids should all be facing out. Repeat this process for the other side.
  • If the red peg won’t fit into the base as you are connecting the second side chain because the hole is on the “wrong side”, unhook the red peg from the other side of that base only and spin the base 180 degrees. Both pegs should now fit in the holes.
  • Make sure that one of the chains has the purple phosphate at the end and ends in a red sugar with the peg exposed and the other chain starts at the bottom with a sugar with it’s red peg exposed and ends in a purple phosphate. This will illustrate the antiparallel nature of DNA.
  • You may have one or two extra pieces. Please check with your teacher.

When you finish, raise your hand so your model can be checked. Your teacher will then instruct you on clean-up.

Then answer the application questions on the following page.

Application:

  1. Where in the cell do you find DNA?
  1. Why is DNA located there (HINT: Why is anything kept “locked up”)?
  1. Describe the process that would be done in order for DNA replication to occur. Make sure to include the following words and phrases in your answer and UNDERLINE these words/phrases where they are being used. (you may use your DNA replication class notes to help you.)

SkillsApplicationsConcepts

5’ to 3’ direction

DNA polymerase

DNA replication

Helicase

Hydrogen Bonds

Lagging strand

Leading strand

Okasaki fragments

Two identical DNA molecules

DNA is unwound and unzipped

SkillsApplicationsConcepts

______

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