Chapter 16 HW

You are working to develop a therapy for patients with a particular disease. The disease involves genes that are misexpressed due to defects in post-transcriptional regulation. What specific process(es) could you target to affect post-transcriptional control of gene expression?

- Splicing of pre-mRNAs - Capping of mRNAs - Polyadenylation of mRNAs - Transport of mRNAs out of the nucleus

The lac repressor is inactivated by binding to which of the following?

Allolactose

Some activators interact directly with RNA polymerase II while others require the assistance of a(n) ________

Coactivator

Enhancers can act at a distance from the gene being transcribed because ___ can form loops.

DNA

In vertebrates, methylation of _____ ensures that once a gene is turned off, it stays off.

DNA

The trp operon consists of ________ genes that encode tryptophan biosynthesis enzymes.

Five

Proteins called _______ transcription factors can initiate transcription only at the basal rate.

General

What is a major disadvantage to a bacterial cell of having an operon?

If there is a mutation in a regulatory region, none of the proteins will be synthesized

How does the cell recognize that lactose needs to be metabolized?

Lactose is converted into allolactose, which inhibits the lac repressor

The lowest level of chromatin structure consists of DNA wrapped twice around a group of histones to form a(n) ________

Nucleosome

At which of the following level(s) can gene expression be regulated in eukaryotes?

Passage of mRNA through the nuclear membrane, destruction of the mRNA, and rate of protein synthesis

RNA polymerase binds to the

Promoter

General transcription factors, along with TAFs, recruit __________ II and position it at the start of the protein-coding sequence.

RNA polymerase

Transcription is carried out by the enzyme

RNA polymerase

Evaluate the statements below and determine which is the best explanation of why bacterial cells use operons and polycistronic RNA

Since proteins in a pathway work together, they should be expressed at the same time and the same level

If lacI were mutated, what effect would this have on lactose metabolism?

The repressor protein would not function properly, and the lac operon would be over expressed

If lacO were mutated, what effect would this have on lactose metabolism?

The repressor would not properly bind to the operator, and the lac operon would be over expressed

Evaluate the statements below and determine which is the best reason for why eukaryotes use basal transcription factors

They allow RNA Polymerase to locate the promoter

Which of the following statement(s) about basal transcription factors is(are) TRUE?

They are essential for transcription and they cannot increase the rate of transcription by themselves

The most efficient control of eukaryotic gene expression is achieved at the level of

Transcription initiation

What level of regulation do eukaryotes possess that prokaryotes do not?

Transport of RNA out of the nucleus

How does the cell regulate the initiation of transcription in eukaryotes?

With activators and repressors

The _________ of histones tends to loosen the coiling of DNA, making it more accessible for transcription.

acetylation

A(n) _________ is a regulatory protein that acts to increase the rate of transcription above the basal rate.

activator

The coding region of a gene is located _______ from its promoter.

downstream

Each specific transcription factor binds to a segment of DNA called a(n) ________

enhancer

Chromatin that contains loosely coiled DNA, which is accessible for transcription, is called ________

euchromatin

Chromatin is present in _________ cells only.

eukaryotic

Chromatin that contains highly condensed DNA which is not being expressed is called ____________

heterochromatin

The structure of chromatin can be modified by altering either the DNA or the _______ attached to DNA.

histones

In the absence of tryptophan, the trp repressor is

inactive and cannot bind to the operator

The lac repressor binds to what site within the lac operon?

lacO

Which of the following is not part of the lac operon?

lacl

Tighter coiling of the chromatin makes the DNA _____ accessible for transcription.

less

The ________ of histones is correlated with tighter coiling of the DNA and inactive regions of chromatin.

methylation

Large chromatin-remodeling complexes alter the structure of chromatin in order to make the DNA _______ accessible to regulatory proteins which, in turn, affect gene expression.

more

Formation of the transcription initiation complex begins when general transcription factors bind to a segment of DNA called the _______

promoter

The formation of nucleosomes may block the binding of transcription factors and RNA polymerase II to the _______

promoter

The correct order of gene expression control mechanisms in eukaryotes is

transcription initiation, transcription elongation, transcription termination, post-transcriptional processing, nuclear export

In the presence of tryptophan, tryptophan binds to the

trp repressor.

The assembly of transcription factors begins

upstream from the transcription start site

In some cells, DNA combines with proteins to form a substance called _______

Chromatin