1.) Explain how combinatorial control makes it possible to havefar fewer transcription factors than the number of genes that aretranscriptionally regulated.
2.) If a miRNA were 5 nucleotides long, what is the chance offinding a complementary sequence in a randomly selected 5nucleotide sequence in mRNA? [Assume mRNA sequences to be randomand that mRNAs have an equal amount of each nucleotide (A, U, G,and C)]. If an miRNA were 10 nucleotides long, what is the chanceof finding a complementary sequence in a randomly selected 10nucleotide sequence in mRNA? If you were designing a syntheticmiRNA to specifically target a particular mRNA, would you want todesign a 5 or 10 nucleotide long miRNA? Why?
3.) In the fungus Neurospora crassa, roughly 2 – 3% of cytosinesare methylated. Researchers isolated Neurospora DNA sequences thatcontained 5-methyl cytosine and found that almost all methylatedsequences were located in inactive copies of transposable elements.On the basis of these observations, propose a possible explanationfor why Neurospora methylates its DNA and why DNA methylation inthis species is associated with transposable elements.
4.) Some cases of bacterial gene regulation involve use ofalternative transcriptional terminators. Propose a plausible waythat a riboswitch could function in the use of alternativebacterial transcriptional terminators.
