Exam 9: Transcriptional Regulation and Epigenetics

Some bacterial genes are regulated by transcriptional activators rather than by repressors.

The lac operon in E. coli is regulated by allolactose, which _______ a(n) _______ of transcription.

Which experimental evidence was not useful in the search for a link between histone acetylation and gene activation?

The table below provides information about RNA strands that were found to be involved in gene regulation in mammalian cells. Which strand(s) would be classified as lncRNAs? RNA strand Length (number of nucleotide bases) Associated proteins I 340 Polycomb proteins, histone deacetylase II 25 none III 57 none IV 215 DNA methylase

lncRNAs assist with changes in chromatin. In embryonic stem cells some of these molecules can act in a repressive role to suppress differentiation and maintain the stem cell state, while others can act in an activating role to allow differentiation to proceed.

The lac operon is regulated by both a positive transcriptional control system and a negative transcriptional control system. Under what conditions will both systems operate to stimulate transcription of the lac operon?

What causes RNA polymerase to pause just after transcription is initiated?

A skin cell and a muscle cell taken from a single mouse differ in appearance and metabolism. If you were to examine the DNA in these two cells, how would they compare?

Looping of DNA has been observed by investigators using electron microscopy techniques. The presence of which feature in DNA might be indicated by such observations?

The Xist lncRNA assists with X chromosome inactivation by binding which protein(s) to facilitate histone modification?

Which is a mechanism of histone change that is mediated by chromatin remodeling factors?

A scientist used a mammalian cell extract to see whether it contained any chromatin remodeling factors. She incubated the cell extract with and without ATP in the presence of chromatin containing promoters X, Y, and Z and tested whether RNA polymerase would bind to any of the promoters. The table below summarizes the results. Do the results suggest that a chromatin remodeling factor was present in the cell extract? RNA polymerase binding Promoter + ATP -ATP Yes No Y Yes Yes No No

A research group characterized regions of DNA within chromatin from mouse cells. They also characterized the histones flanking these regions. The table below summarizes some of their results. DNA region DNAse sensitivity of region Modification of nearest histone I Yes Monomethylated lysines II Yes Trimethylated lysines III No None IV Yes Monomethylated lysines Which statement provides a plausible hypothesis based on these data?

Which molecule has a critical role in transcription elongation?

A research lab working with mouse cells characterized three mutant cell lines summarized in the table below. Which of these is most likely to contain a mutated form of P-TEFb? Explain. Mutant cell line Transcription initiation Transcription elongation Histone modification Functions normally Unable to make transcripts larger than 50 nucleotides Functions normally Lost sensitivity to a transcriptional repressor Functions normally Functions normally Functions normally Functions normally Lost ability to deacetylate histones

The light micrograph image below shows a section of a Drosophila chromosome. The arrows indicate regions containing histones that have been deacetylated.

How are lncRNAs similar to miRNAs?

How do repressors differ from activators of transcription in bacteria?

A researcher wants to isolate regulatory sequences of DNA bound to their transcription factors. She then wants to sequence the DNA fragments that form the binding sites that the transcription factors recognize and bind. Which technique should the researcher use for her first step?

Which molecule provides a source of energy used by chromatin remodeling factors to alter DNA−histone interactions?