Describe the difference between introns and exons.

The following is a portion of an mRNA sequence:

3'-AUCGUCAUGCAGA-5'

During transcription, was the adenine at the left-hand side of the sequence the first or the last nucleotide used to build the portion of mRNA shown? Explain how you know.

Compare and contrast the properties of DNA polymerase and RNA polymerase, listing at least three similarities and at least three differences between the molecules.

The DNA sequences shown below are from the promoter regions of six bacterial genes. In each case, the last nucleotide in the sequence (highlighted in blue) is the nucleotide that initiates transcription. Examine these sequences and identify the Pribnow box sequence at approximately -10 for each promoter.

What is the role of enhancer sequences in transcription of eukaryotic genes? Speculate about why enhancers are not part of transcription of bacterial genes.

For a eukaryotic gene whose transcription requires the activity of an enhancer sequence, explain how proteins bound at the enhancer interact with RNA pol II and transcription factors bound at the promoter.

Three genes identified in the diagram as A, B, and C are transcribed from a region of DNA. The 5'-to-3' transcription of genes A and C elongates mRNA in the right-to-left direction, and transcription of gene B elongates mRNA in the left-to-right direction. For each gene, identify the coding strand by designating it as an 'upper strand' or 'lower strand' in the diagram.

Compare the control of gene regulation in eukaryotes and bacteria at the level of initiation of transcription. How do the regulatory mechanisms work? What are the similarities and differences in these two types of organisms in terms of the specific components of the regulatory mechanisms?

The eukaryotic gene Gen-100 contains four introns labeled A to D. Imagine that Gen-100 has been isolated and its DNA has been denatured and mixed with polyadenylated mRNA from the gene.

Are intron regions single stranded or double stranded? Why?