13: Regulation of Gene Expression Flashcards by Laura Orzechowski

The process of converting genetic information into a genetic product (usually a protein) is…

Gene expression

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Prokaryotes regulate their gene expression to…

Respond to environmental changes

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Eukaryotes regulate their gene expression to…

Progress through developmental stages and maintain homeostasis

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List the three means by which organisms can regulate gene expression.

Transcriptional regulation
Post-transcriptional regulation
Post-translational regulation

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Which method(s) of regulation can only occur in eukaryotes?

Post-transcriptional

because this occurs as mRNA is moved out of the nucleus, which prokaryotes do not have

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The first opportunity for cells to control gene expression is…

Transcriptional regulation

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The most common form of regulation in cells is…

Transcriptional

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Transcriptional regulation depends on…

RNA polymerase interacting with DNA

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Transcriptional regulation is controlled by…

Binding proteins
(“transcription factors”)

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The ____ contains the binding site for regulatory proteins that affect the cell’s ability to perform transcription.

Promoter

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The region of the promoter where RNA polymerase binds to the DNA is the…

Core promoter

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Proteins that affect the ablity of RNA polymerase to bind to the promoter or start transcription are…

Regulatory proteins

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True or false:

In eukaryotic cells, each gene has its own promoter sequence.

True

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True or false:

In prokaryotes, a single promoter can control multiple genes.

True

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Regulatory proteins that help recruit RNA polymerase to start transcription are called…

Transcriptional activator proteins

(or simply “activator proteins”)

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The process by which a regulatory protein promotes transcription is…

Positive control

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A protein that binds to a gene in such a way as to prevent RNA polymerase from binding is called a…

Transcriptional repressor protein

(or simply “repressor protein”)

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The process by which a regulatory protein inhibits transcription is…

Negative control

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True or false:

Genes can have positive or negative control, but not both.

False

A gene or operon can have positive control, negative control, or both.

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A cluster of genes with related functions that are controlled by a single promoter is called a(n)…

Operon

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Prokaryotes are able to respond quickly to environmental changes because…

Their genes are organized into operons

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List the three regions that an operon may have.

Core promoter
Activator binding site
Operator

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The ____ region of an operon is bound by the sigma factor of RNA polymerase.

Core promoter

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True or false:

All operons have a core promoter region.

True

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The DNA binding site for an activator protein is called the...

Activator binding site

# True or false: All operons have an activator binding site.

False Only operons that exhibit positive control can have activator binding site(s).

The DNA binding site for a repressor protein is called a(n)...

Operator

# True or false: All operons have an operator.

False Only operons that exhibit negative control can have operator(s).

In prokaryotes, the proteins needed for lactose metabolism are encoded in the...

*lac* operon

What type(s) of control does the *lac* operon exhibit?

Positive and negative

In the *lac* operon, the CAP activator promotes transcription when...

Lactose is present

In the *lac* operon, the lac repressor protein inhibits transcription when...

No lactose is present

The *lac* operon can only perform transcription when...

Lactose is present AND glucose is absent

What happens in a *lac* operon when both lactose and glucose are present?

The lac repressor is released, but the CAP activator does not bind to the DNA. ## Footnote because glucose is the cell's preferred food source

The *trp* operon contains all the genes needed to produce...

Tryptophan (an amino acid)

What type(s) of control does the *trp* operon exhibit?

Negative

The *trp* operon does not perform transcription when...

Tryptophan is present in the environment

The *trp* operon performs transcription when...

No tryptophan can be acquired from the environment

How does the *trp* operon exhibit negative control?

When tryptophan is present, it binds the the trp repressor protein, enabling it to bind to the operator sequence.

____ occurs when transcription is stimulated by molecules in the environment.

Induction

____ occurs when transcription is inhibited by molecules in the environment.

Repression

In addition to positive and negative control, the *lac* operon exhibits...

Induction ## Footnote (the presence of lactose causes the lac repressor protein to be released from the DNA)

In addition to negative control, the *trp* operon exhibits...

Repression ## Footnote (the presence of tryptophan causes the trp repressor protein to bind to the DNA)

Induction and repression occur when...

An external molecule causes or stops transcription by interacting with a regulatory protein

Positive and negative control refers to...

The type of protein that regulates transcription

List the two types of transcription factors.

1. General 2. Specific

# True or false: General transcription factors are only found in eukaryotes.

True

Eukaryotes require general transcription factors in order for...

The minimum (basal) amount of transcription to occur

List three ways eukaryotes can use general transcription factors to regulate transcription.

1. Changing the availability of the transcription factors 2. Altering the TFs' ability to bind to DNA 3. Altering the TFs' ability to interact with RNA polymerase

____ are needed to increase transcription past the basal level.

Specific transcription factors

# True or false: Specific transcription factors are found in both prokaryotes and eukaryotes.

True

# True or false: A specific transcription factor will always bind at or near the core promoter.

False Eukaryotes in particular may utilize other binding sites.

Some specific transcription factors bind to DNA regulatory regions called...

DNA enhancer elements

Why do specific transcription factors not always bind to the core promoter in eukaryotes?

Their genomes are much bigger.

In eukaryotes, DNA and histone proteins are packaged into bead-like structures called...

Nucleosomes

Nucleosomes are then assembled into...

A chromatin structure

Why do eukaryotes package their DNA?

So that all the DNA is able to fit into the nucleus.

When DNA becomes wound around histone proteins, it becomes ____ for transcription machinery to access it.

Harder

____ can be modified to change how tightly DNA is wound around them.

Histone proteins

____ is a process that loosens DNA by adding an acetyl group.

Acetylation

The structure of nucleosomes can be altered by...

ATP-dependent enzymes

List three ways in which ATP-dependent enzymes can change nucleosomes.

1. Sliding 2. Moving up/down DNA 3. Remodeling

Remodeling involves altering...

How DNA interacts with histone proteins

____ regulation occurs while the cell is preparing mRNA for translation.

Post-transcriptional regulation

Which type of gene regulation only occurs in eukaryotes?

Post-transcriptional

List four methods of post-transcriptional gene regulation.

1. mRNA alternative splicing 2. Inhibition of transport from nucleus 3. Inhibition of translation 4. mRNA regulation by small RNAs

Alternative splicing is the process of...

Causing one mRNA to code for different proteins

Some mRNA sequences can be spliced in multiple ways, enabling them to...

Code for more than one protein

Alternative splicing has been observed in the...

Thyroid and hypothalamus

It is believed that only around ____% of the mRNA produced is exported and translated.

List two ways that the cell can limit the amount of mRNA that is translated after it has left the nucleus.

1. Limiting the availability of proteins needed for translation 2. Producing proteins that prevent specific mRNA from being translated

List the two classes of small RNAs that can interfere with mRNA translation.

1. Micro RNAs (miRNAs) 2. Small-interfering RNAs (siRNAs)

Micro RNAs are formed when a single-stranded RNA folds to make a small segment of...

Double-stranded RNA

Micro RNA strands are...

Self-complementary

Micro RNAs are usually encoded in the...

Genome

Small-interfering RNAs are made from long segments of double-stranded RNA that are...

Cut into small segments

List two ways in which siRNAs can be formed.

1. Produced by the cell through pairing of 2 mRNAs 2. Introduced from the environment

Small RNAs interact with proteins to form a complex called...

RISC

After binding to the complementary region on a target mRNA, the proteins in RISC...

Block translation or degrade the mRNA

____ is a research method that introduces specific segments of double-stranded RNA to selectively control gene expression.

RNA interference (RNAi)

RNAi allows researches to analyze the effects of ____ on an organism.

Gene loss

Post-translational gene regulation involves... | (two items)

1. Modification of proteins 2. Degradation of proteins

Post-translational regulation occurs...

After mRNA has been made into proteins

List three methods of modifying proteins.

1. Adding/removing a phosphate group 2. Adding carbohydrates 3. Adding lipid groups

The addition or removal of a phosphate group is especially important for...

Enzymes

The addition or removal of a phosphate group is called...

Phosphorylation or dephosphorylation

The addition of carbohydrates is especially important for...

Cell identity proteins

The addition of a carbohydrate is called...

Glycosylation

The addition of lipid groups is especially important for...

Anchor proteins in the cell membrane

Cells can systematically target and degrade proteins by...

Adding ubiquitin

After a protein has been ubiquinated...

It is broken down into polypeptide fragments by the proteasome

# True or false: The ubiquitin is also degraded by the proteasome.

False It is cleaved from the protein and released to be used again

Because of regulation, gene expression is...

Very tightly controlled

Transcriptional regulation controls...

Which genes are transcribed

Transcriptional regulation is performed by...

Transcription factors and the accessibility of DNA

Post-transcriptional regulation controls...

Which genes are translated

Post-transcriptional regulation is performed by...

mRNA processing and translation inhibition

Post-translational regulation controls...

The activity of translated proteins

13: Regulation of Gene Expression Flashcards

Module 3, Lesson 2 (99 cards)