From Gene to Protein—Transcription and Translation



From Gene to Protein—Transcription and Translation

Answer Sheet

Introduction

1. What is a gene? State the definition, and give some examples of genes.

2. What is a protein? State the definition, and give some examples of proteins.

3. Complete the following table to summarize the basic characteristics of transcription and translation.

| |Original message or instructions in: |Molecule which is |Location where this takes |

| | |synthesized |place |

|Transcription |DNA | |Nucleus |

|Translation | | | |

4. What is hemoglobin?

5. Complete the following sentence to describe how differences in a gene can result in normal hemoglobin vs. sickle cell.

Differences in the sequence of _____________________ in the gene result in differences in the sequence of ______________________ in mRNA which result in differences in the sequence of _______________________ in the protein which result in normal vs. defective protein to oxygen which results in normal oxygen transport vs. sickle cell.

Transcription

6. How does the information in the DNA of the gene get copied into a message in the mRNA? Draw a diagram showing the process on transcription that your just explained.

7. Complete the chart that summarizes the base-pairing rules for transcription:

|DNA nucleotide |Complementary nucleotide in RNA |

| G | |

| C | |

| T | |

| A | |

8. Notice that the process of transcription is similar to the process of DNA replication. What are some similarities between transcription and DNA replication?

9. There are also a few important differences between DNA replication and transcription. Fill in the blanks in the following table to summarize these differences.

|DNA replication |Transcription |

|The whole chromosome is replicated. | |

|DNA is made. |mRNA is made. |

|DNA is double-stranded. |mRNA is_______________. |

|DNA polymerase is the enzyme which carries out DNA replication. |________ polymerase is the enzyme which carries out |

| |transcription. |

|T = thymine is used in DNA, |T = thymine is replaced |

|so A pairs with T in DNA. |by ____ = uracil in RNA, |

| |so A in DNA pairs with _____ in mRNA. |

10. After completing the transcription modeling procedure, summarize what you have learned by explaining an mRNA molecule is created. Include in your explanation the words and phrases: base-pairing rule, complementary nucleotides, cytoplasm, DNA, gene, messenger RNA, nucleotide, nucleus, and RNA polymerase.

Translation

11. In the diagram below, circle the anti-codons in the tRNA molecules in the figure. Describe how the anti-codon is used to determine which amino acid should be attached to the growing protein chain.

12. Complete the table below that shows the codons in your mRNA and the corresponding amino acids. Use the base-pairing rule to show the tRNA anti-codon for each mRNA codon.

|Amino acid |mRNA codon |Anti-codon in tRNA molecule |

| | |that carries this amino acid |

|Threonine (Thr) | ACU | |

|Histidine (His) | CAU | |

|Proline (Pro) | CCU | |

|Leucine (Leu) | CUG | |

|Glutamic acid (Glu) | GAG | |

|Valine (Val) | GUG | |

13. At the beginning of the translation modeling procedure, your model should have look like this.

14. What is the function of mRNA?

15. What is the function of tRNA?

16. Explain how tRNA and mRNA work together to put the right amino acids in the right sequence as the protein is synthesized.

17. The proteins in biological organisms include 20 different kinds of amino acids. What is the minimum number of different types of tRNA molecules that must exist in the cell?

18. What part of translation depends on the base-pairing rules?

19. Explain why it makes sense to use the word translation to describe the change from mRNA to a protein.

20. To summarize what you have learned about translation, explain how an mRNA molecule directs the synthesis of a protein. Include in your answer the words amino acid, anti-codon, codon, mRNA, protein, ribosome, tRNA, and translation. (you can use the back ( )

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a) What happened to the first tRNA? Why isn't it shown in this diagram?

b) Draw a rectangle around the third codon in the messenger RNA.What is the anti-codon for that codon?

c) Which amino acid will be the third amino acid in the hemoglobin protein?

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