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					DNA Molecule Lab

Name ________________________________ Hour__________ Date __________________

Problem: What are the parts of a DNA molecule and what does it look like? Background Information:  In most living organisms the carrier of the genetic information is deoxyribonucleic acid (DNA).  The intricate structure of the DNA molecule carries the genetic code for inherited characteristics from one generation to the next.  The DNA molecule consists of thousands to millions of nucleotides bonded together in an interconnected chain.  Nucleotides have three components: a sugar molecule, a phosphate group, and a nitrogenous base.  In DNA the sugar is a five-carbon molecule called deoxyribose.  The deoxyribose sugars are linked together by phosphate groups at the number three and number five carbons of the sugars.  The number three carbon end, or three-prime (3’) position, of one sugar is bonded by the phosphate group to the number five carbon, or 5’ position, of another sugar.  The process is repeated to form very long polynucleotide chains.  The DNA molecule has as its structural backbone two antiparallel sugar-phosphate chains.  The two single strands of DNA are interconnected via hydrogen bonds between nitrogenous bases. Of the four nitrogenous bases, adenine (A) and thymine (T) bond together and cytosine (C) and guanine bond together.  It is this strict base pairing between strands that dictate the spiraling DNA structure known as the double helix. NUCLEOTIDES Materials: Kit of DNA colored construction beads. Deoxyribose Sugar = White red Phosphate Group = Red Nitrogen Bases white Adenine = Yellow yellow Guanine = Green red Thymine = Blue Cytosine = Orange white Hydrogen Bonds = Clear connectors/or black connectors blue PROCEDURE: Construction of nucleotides 1. Attach a phosphate (red) to each of the deoxyribose sugar (white) molecules at the 3’ position. The red bead (phosphate molecule) is the top bead and the white (sugar bead) is the bottom bead. 2. Attach one nitrogen base ( blue, yellow, green or orange) to each of the sugar-phosphate molecules at the sugar molecules 1’ (side hole) position. A nucleotide consists of one white beads, one red bead and one of the other colored beads. (See diagrams above.) 3. Sort your nucleotides into four piles according to the base they contain. You should have 8 nucleotides that contain a red, white and yellow bead. This is an adenine nucleotide. You should have 8 guanine (green) nucleotides, 8 thymine (blue) nucleotides and 8 cytocine (orange) nucleotides.

Assembly of DNA molecule 4. Take one half (4) of each of the types of nucleotides and set them aside for later use (16 total). Set aside 4 guanine (green) nucleotides, 4 cytocine (orange) nucleotides, 4 adenine (yellow) nucleotides and 4 thymine (blue) nucleotides. 5. Mix up the other half (16 total) of the nucleotides. Next make a chain of nucleotides. Begin construction by connecting the red and white beads of two of your nucleotides. Continue adding to the chain until you have connected all sixteen of the nucleotides. It doesn’t matter what order you have them in. 6. This is half of a DNA molecule, a long chain of 16 nucleotides. Lay it vertically on your table. Face all of the nitrogen bases to the right.
R W R W R

……………………..
bases

7. From the nucleotides that you had set aside, select a nucleotide whose nitrogen base should bond to the first nucleotide in your chain (check on the proper bonding requirements) Adenine always bonds to Thymine and cytosine always bonds to guanine. Therefore, blue always bonds to yellow and orange always bonds to green. 8. Lay it along side your chain and connect the bases together using a hydrogen bond. On this side of your molecule be sure that the 5’ position of the sugar faces upwards and the base faces to the left. Your molecule must have antiparallel chains. ……………………..

adenine thymine hydrogen bonds cytosine guanine

9. Next select another nucleotide from your set-aside group, whose base should bond to the next nucleotide in your chain. Using a hydrogen bond connect it in the same orientation. After you have bonded the nitrogen bases connect the sugar and phosphate molecules for the two nucleotides. 10. Continue on, connecting the remaining nucleotides, from your set-aside group, until your molecule is completed. You should have two strands of nucleotides bonded together at their nitrogen bases. It looks like a ladder. The sides of the ladder are phosphate and sugar molecules and the steps of the ladder are the nitrogen bases.

DNA Molecule Lab

Name______________________________________ Hour__________ Date _______________________

Problem: What are the parts of a DNA molecule and what does it look like?
Analysis Questions Have your teacher observe and approve your molecule before continuing. __________________ signature teacher 1. Draw your molecule, labeling or coloring all of its parts. Use the letters A,T,C,G, P and S.

2. Where is the deoxyribose sugar molecule located in your model of DNA? 3. What role does the phosphate molecule play in the structure of DNA? 4. What are the three parts of a nucleotide? ___________________________________________________ 5. How many nucleotides are in your model molecule? _________________________________________ 6. Where are the nitrogen bases located in your molecule? _______________________________________ 7. How many different types of nitrogen bases are there in a DNA molecule? _________________________ 8. How do the nucleotides differ from each other? _______________________________________________ 9. If a molecule of DNA contained 8 parts of guanine, how many parts of cytosine would it contain?________ 10. What is the relationship between the bases adenine and thymine in a DNA molecule? ________________ _____________________________________________________________________________________ 11. How many groups in your class made a DNA molecule exactly like yours? (Hint: you will have to walk around the room and check the other models.) _______________________________________________ 12. How many nucleotides are in a real molecule of DNA? (Hint: check in your book.) ___________________ 13. Find the picture of DNA in your book and explain why adenine only bonds to thymine and cytosine only bonds to guanine. ______________________________________________________________________ 14. What is the function of DNA? _____________________________________________________________ _____________________________________________________________________________________ 15. What are antiparallel chains? _______ _____________________________________________________ _____________________________________________________________________________________ CONCLUSION: What are the parts of a DNA molecule and what does it look like? ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________


				
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