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Ashley W-Candy DNA models

Lesson Plan for High School Biology

Duration: 1 class period (55 minutes)

California Content Standards Addressed:

5. The genetic composition of cells can be altered by incorporation of exogenous DNA into the cells. As a basis for understanding this concept:

            a. Students know the general structures and functions of DNA, RNA, and protein.

            b. Students know how to apply base-pairing rules to explain precise copying of DNA during semi conservative replication and transcription of information from DNA into mRNA.

Materials:

Each group will receive a DNA model lab and a bag that contains:

Licorice chunks (red and black) – 2 long pieces, one of each color

Mini Gummy Bears or marshmallows (4 different colors) – 6 total

Wooden toothpicks – 3

2 8-inch pieces of durable string

Procedure

Each group (2-3 students each) will

1. Assign one nitrogen base to each of the four colors of the Gummy bears.

Adenine =_________________

Thymine =_________________

Cytosine=_________________

Guanine =__________________

 

2. What does the black Licorice represent? ____________________________

 

3. What does the red Licorice represent? ______________________________

 

4. What structure is formed from a red Licorice, a black Licorice and a gummy bear?

____________________________________________________

 

5. Prepare your sugar-phosphate backbone for your DNA, by stringing alternating colors of licorice (red, black, red, etc.) along each piece of string until you have 6 pieces total per string. Make sure you have knotted off one end of each of the two strings. Remember: You need two sugar-phosphate chains.

 

6. Which combinations bases form the complimentary base pair “rungs” of DNA? ____________________________________________________

 

7. Using # 1 and # 6 as your guides, we need to start base pairing! You will do this by taking two nitrogenous bases (gummy bears/marshmallows) that are complimentary and inserting the toothpick through both of them, so that they are centered in the toothpick. Then insert one end of the toothpick into the first sugar group on one of your backbone chains. The other end of the toothpick should be inserted into the same sugar on the opposite strand. Continue doing this with all of your nitrogenous bases until you have used up all of your toothpicks and bases.

 

Student Prior Knowledge:

Students have previously studied cell structure and function of the organelles within Eukaryotic cells.

Students have previously studied the structure and function of DNA

Students have been introduced to DNA replication and know that it is a semi-conservative process

Students know the base pairing rules

Explanation:

The lab is designed to help students put together their own DNA model in a fun way. The lab is done after the students have learned about DNA and DNA replication, but prior to transcription and translation. The lab can be used for DNA replication as well if you have the students keep their models in their bags and then supply them with extra materials for their new leading and lagging strands. It provides students a chance to reason through the arrangement of their base pairs and nucleotides and gets them thinking about how DNA replication might take place. 

Photos:

These photos are not from my own lab, but from http://library.thinkquest.org/19037/making_a_candy_model.html

and...if you wanted to use this model to go on and replicate you can...




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Norman Herr,
Mar 17, 2011, 9:48 AM
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Norman Herr,
Mar 17, 2011, 9:56 AM
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