Cells, Genes & Molecules

You are to write a three-part essay by answering the questions given below.
To write this essay, the questions within each section do not have to be answered in the order given below. Your essay should have a good flow of ideas as you answer these questions.

PART A: Arabinose operon (approximately 1,000 words)

1. Define the term “operon”
2. What is the general function of the arabinose operon?
3. What is arabinose used for by the bacterial cell?
4. What is the function of each region/gene within the operon?
5. Draw a detailed schematic diagram of the arabinose operon showing all of the molecular features of each region within the operon. The drawing does not have to be to scale.
6. What is the sigma factor that binds to each promoter of the operon?
7. Describe the negative control of the arabinose operon.
8. Describe the positive control of the arabinose operon.
9. Using the questions below, describe what would happen if there was a loss of function frameshift mutation in the coding region of the control gene.
   a. Would the control gene be transcribed? Explain your answer
   b. Would the control gene be translated? Explain your answer
   c. Would the structural genes be transcribed? Explain your answer.
   d. Would the structural genes be translated? Explain your answer.
10. Compare the arabinose operon with the lactose operon in terms of structure and function.
    PART B: Control of eukaryotic gene expression – Effect of mutation (approximately 500 words)
    In a eukaryotic cell, a single nucleotide deletion has occurred in the coding region of the gene encoding the polyA binding protein. Answer the following questions.
11. By answering the questions below, describe effect of such a mutation on the expression of the polyA binding protein gene.
    a. Would the gene be transcribed? Explain your answer.
    b. Would it be translated? Explain your answer.
    c. What would be the effect of such a mutation on the protein? Explain your answer.
12. By answering the questions below, describe what would happen to other genes in the genome of a eukaryotic cell.
    a. Would you expect them to be transcribed? Explain your answer.
    b. Would you expect them to be translated? Explain your answer.
13. Briefly describe what would happen to a eukaryotic cell if such a deletion occurred.

PART C: Control of eukaryotic gene expression -miRNA (approximately 500 words)
The model organism Caenorhabditis elegans is a roundworm and is frequently used to understand function of eukaryotic genes. The genome of C. elegans encodes a microRNA (miRNA) called lin4 – the first miRNA ever discovered. The lin-4 miRNA controls the expression of a gene called lin-14, which is involved in the development of C. elegans. Using the miRNA lin4 as the example, answer the following questions:

1. What is a miRNA?
2. Where within a cell does a miRNA control gene expression?
3. Describe the steps involved in creating a miRNA.
4. Describe how lin-4 regulates the expression of the lin-14 gene.
   a. Does lin-4 miRNA bind to the lin-14 gene, its hnRNA or its mRNA?
   b. Where within the lin-14 sequence does lin-4 bind?
   c. How does the binding of lin-4 influence the expression of the lin-14 gene?
5. Briefly discuss why this regulation is important.