Protein Synthesis: Transcription and Translation

Purpose: To identify the molecules involved in protein synthesis; to model the process of protein synthesis.

Materials: Protein synthesis kit Deoxyribose – black pentagon Ribose – purple pentagon Phosphate – white tube Hydrogen bond – white rod Bases – Cytosine – blue tube Thymine – green tube Adenine – orange tube Guanine – yellow tube Uracil – purple tube tRNA – purple stick Amino acids – black sticks Peptide bonds – gray tubes

Procedure:

Part I. Constructing a DNA molecules

1. Build 18 nucleotides for a DNA molecule. A nucleotide of DNA consists of a phosphate, deoxyribose sugar, and one of four bases (A, T, C, or G). 2. Use these nucleotides to construct a DNA molecule that is 9 nucleotides in length. Connect the bases using hydrogen bonds. Be sure bases are paired according to base pairing rules. 3. On your data sheet, list the sequence of bases found along each side of your DNA molecule. Answer the questions that follow.

Part II. Transcription

1. Place your constructed DNA molecule on your desk. 2. Construct 9 mRNA nucleotides. A nucleotide of mRNA consists of a phosphate, ribose sugar, and one of four bases (A, U, C, or G). 3. Unzip your molecule of DNA. 4. On your data sheet, list the sequence of bases found along the left side of your DNA molecule. 5. Bond the mRNA nucleotides with their partners on the left side of your DNA (using hydrogen bonds) and to each other (connect sugars and phosphates). 6. Remove the constructed mRNA molecule from the DNA template. Zip the two strands of DNA nucleotides back together. 7. On your data sheet, list the sequence of bases on your mRNA molecule. Answer the questions that follow. Part III. Translation

1. Place the ribosome molecule on your desk. 2. Place the mRNA molecule on the ribosome. 3. Attach the three tRNA molecules to the amino acid molecules that match. 4. On each of the three tRNA molecules, attach bases that are complimentary to the bases on the mRNA molecule. For example, if the first three bases on mRNA are AUG, the bases UAC should be placed on the tRNA. 5. Bring the first tRNA molecule to the first codon (group of three nucleotides) on the mRNA molecule. Attach with hydrogen bonds. Be sure the bases pair according to the base pairing rules. 6. Move the ribosome down to the next codon along the mRNA molecule. Attach the next tRNA to the second codon with hydrogen bonds. Be sure the bases pair according to the base pairing rules. 7. Connect the two amino acids with peptide bonds (gray tubes). 8. Move the ribosome down to the third codon along the mRNA molecule. Bring the third tRNA molecule to the last codon along the mRNA molecule. Attach the two with hydrogen bonds. Again, be sure bases pair according to base pairing rules. 9. Connect the second and third amino acid with a peptide bond. 10. Answer the questions on your data sheet. 11. Disconnect the polypeptide (chain of amino acids) from the tRNAs. 12. Disconnect the tRNA molecules from the mRNA molecules. 13. Remove the mRNA molecule from the ribosome. 14. Answer the questions on your data sheet. Data Sheet: Protein Synthesis

Part I. DNA molecule

1. List the sequence of bases along the left side of your DNA molecule.

2. List the sequence of bases along the right side of your DNA molecule.

3. How do the bases pair together in your DNA molecule?

4. What holds the bases together in your DNA molecule?

5. What structures are found along the sides of the DNA ladder? Which one attaches to the bases?

Part II. Transcription

6. List the sequence of bases along the left side of your DNA molecule.

7. List the sequence of bases along your mRNA molecule.

8. How do the bases pair together while the mRNA molecule is being constructed?

9. How do these base pairing rules differ from the base pairing rules for a molecule of DNA?

10. Where in the cell is this process taking place?

11. Where in the cell will the mRNA molecule go once it has been constructed?

12. Why is mRNA needed?

13. Besides the base pairing rules, how else does this mRNA molecule differ from the DNA molecule constructed? Part III. Translation

14. What is the name of the group of three nucleotides on the mRNA molecule?

15. What is the name of the group of three nucleotides on the tRNA molecule?

16. How do the bases on the mRNA codon and tRNA anticodon compare?

17. Where in the cell does this process of translation take place?

18. What molecules are being made during translation?

19. Why does an organism need those molecules named in number 18?

20. What molecules are linked together during translation to make the molecules named in number 18?

21. How are those molecules named in number 20 held together? Analysis Questions

1. If one-half of the DNA sequence is AGTCTTACTGTT, then what would the sequence of bases along the complimentary strand of DNA be?

2. Using the DNA sequence from number 1, what would be the complimentary base sequence produced on an mRNA strand made from this DNA strand?

3. The name of this process in which mRNA is constructed using DNA as a template is called what?

4. Where does this process named in #3 take place?

5. Why is this process named in #3 necessary?

6. If the mRNA codons are AUG, GGU, and CAG, what three tRNA anticodons would pair with them?

7. Amino acids are brought to the ribosome by what molecule?

8. Amino acids will be linked together by peptide bonds to form what molecules?

9. The process in which these amino acids are linked together at the ribosome, with the help of tRNA and mRNA molecules is called what?

10. What will the body use these molecules produced during the process named in #9 to do?