Download DNA Structure LAB

Name: ___________________________________________________________________ LAB-­‐ THE STRUCTURE OF DNA & RNA OBJECTIVES: • To develop an understanding of the structure of DNA and RNA. • To learn how the structure of these molecules permit them to carry out their function. MATERIALS: Each table needs: Paper models and an envelope with free-­‐floating nucleotides. PROCEDURE: PART A. Constructing a Model of DNA 1. Gather the following DNA nitrogenous base models: BASE COLOR Thymine Yellow Adenine Blue Cytosine Orange Guanine Green 2. Gather the following: phosphate models made from HOT PINK paper and sugar models made from WHITE paper. 3. Push a base, phosphate, and a sugar molecule together to make nucleotide models as shown below: 4. Construct a DNA model using the thymine, adenine, cytosine, and guanine nucleotide models. Make sure the sugar you use is deoxyribose. Remember that DNA is a double chain of molecules connected by the nitrogen bases. Each nucleotide model must fit into another like puzzle pieces. 5. Using the letters A, T, C, and G for the bases, record the order of each nitrogen base below. Our DNA Model Left Strand Right Strand PART B. DNA Replication 1. Place the model of DNA from Part A on your table. Scatter the free-­‐floating DNA nucleotides (in the envelope) around the DNA model. These nucleotides represent the free-­‐floating nucleotides found in cells. 2. Slowly separate the top two nitrogen bases of the DNA model. Continue to separate the nitrogen bases until you reach the end of the molecule. 3. Match the free-­‐floating nucleotides with the nitrogen bases of each side of the split DNA molecules. Using the letters A, T, C, and G for the bases, record the order of each nitrogen base below. Replicated DNA Molecule 1st Molecule 2nd Molecule Left Right Left Right PART C. Transcription (mRNA) 1. Reassemble the model of DNA from Part A. Leave the free-­‐floating nucleotides on the table. 2. Slowly separate the top two nitrogen bases of the DNA model. Continue to separate the nitrogen bases until you reach the end of the molecule. 3. Match the free-­‐floating RNA nucleotides with the nitrogen bases on the left hand side of the split DNA molecules. Match the RNA nucleotides until you reach the bottom of the DNA model. You are now transcribing your DNA template. 4. When the strand of mRNA is complete, separate mRNA from its DNA template. Notice that the sugar used in mRNA is ribose. 5. Using the letters A, U, C, and G for the bases, record the order of each nitrogen base for mRNA below. OUR mRNA OBSERVATION & CONCLUSIONS: PART A. Constructing a Model of DNA 1. Which nitrogen bases pair to form the rungs of the DNA double helix? 2. What are the two molecules that alternate to form the sides of the DNA molecule? 3. What is the relationship between a nucleotide and a molecule of nucleic acid? PART B. DNA Replication 1. How does DNA ensure exact copies are made during replication? 2. What are hydrogen bonds? PART C. Transcription (mRNA) 1. In what three (3) ways do DNA and RNA molecules differ? 2. Explain in detail how mRNA is formed. What is this process called?