BIO 155 Chapter 16

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

Allolactose

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

A study of the effects of damaging toxins on cells and tissue identifies ubiquitin as a key molecule. Can you explain why ubiquitin would be associated with toxin damage?

Damaged proteins are tagged with ubiquitin for degradation.

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

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

RNA polymerase II

Transcription is carried out by the enzyme

RNA polymerase.

Evaluate the statements and determine which is the best explanation for why eukaryotes use so many regulatory elements, such as activators, repressors, coactivators, and basal transcription factors.

The complexity allows specific control over the timing and quantity of the protein produced.

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

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

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

Which of the following statements about general (basal) transcription factors is TRUE?

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

Which of the following statements about enhancers is TRUE?

They are sequences to which activators bind.

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

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

chromatin

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

coactivator

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

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

general

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

histones

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

lacO

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

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

nucleosome

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

RNA polymerase binds to the

promoter.

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

transcription initiation