UNLV biology 196 Chapter 12

Place the steps in gene expression in correct order from first to last.

1- Convert chromatin to an open conformation 2- Transcribe the gene 3- Process the RNA and export from the nucleus 4- Make the protein via translation

Rank the following organisms in order of increasing genome size, starting with the one with the lowest on top.

1. Bacterium 2. Yeast 3. C. elegans (worm) 4. Fruit Fly 5. Human

Rank the different types of mammalian hemoglobins in terms of oxygen affinity, starting with the one that has the highest.

1. Embryonic hemoglobin 2. Fetal hemoglobin 3. Adult hemoglobin

Arrange the stages of development in mammals in order, from the earliest stage (at the top of the list) to the latest stage (at the bottom of the list).

1. Fertilization 2. Embryonic Stage 3. Fetal Stage

Which of the following accurately describe the role of chromatin packing in the expression of eukaryotic genes?

1. Tightly packed chromatin is difficult to transcribe 2. Loosely packed chromatin allows transcription factors and RNA polymerase to access the promoter site and transcription can take place.

What is an operon?

A cluster of genes under the transcriptional control of a single promoter

Select the two ways that a repressor can interact with a GTF to inhibit transcription.

A repressor can inhibit assembly of the pre-initiation complex. A repressor can prevent binding of the TFIID to the TATA box.

When ________ proteins bind to DNA, they increase the rate of transcription.

Activator

Match each term with the correct description.

Activators - proteins that bind to DNA and increase transcription. Enhancers - DNA sequences that increase transcription Repressors - proteins that bind to DNA and inhibit transcription silencers - DNA sequences that prevent transcription

The process whereby different transcripts are made from a single gene is called _______ ________.

Alternative splicing

What is a repressible operon?

An operon that can be repressed by the presence of a small effector molecule.

Match each protein expressed by the lac operon and its function in the breakdown of lactose.

B-galactosidase - Break down of lactose into galactose and glucose Lactose permease - transport of lactose across the cell membrane galactoside transacetylase - covalent modification of lactose and lactose analogues.

Which of the following factors help to increase transcription levels in Eukaryotes?

Binding of an activator protein to DNA Loosening of chromatin structure

Which of the following are ways by which chromatin-remodeling complexes change chromatin structure?

Binding to chromatin and changing the positions of nucleosomes Changing the composition of nucleosomes by replacing standard histones with histone variants. Evicting histone octamers, thereby creating gaps where no nucleosomes are found.

How does the histone code play a key role in transcription?

By attracting proteins that affect gene transcription.

Which of the following statements about genomes and proteomes is True?

Cells of an individual have the same genome, but different proteomes.

DNA and its associated proteins form a compact structure called:

Chromatin

Proteins that use energy from ATP hydrolysis to change the location and compositions of nucleosomes are called ATP-dependent __________-__________ complexes.

Chromatin; remodeling

Most eukaryotic genes, particularly those found in multicellular species, are regulated by many different factors. This phenomenon is called ___________ control.

Combinatorial

In eukaryotes, which base is commonly methylated in DNA?

Cytosine

At the level of transcription, there are several common factors that contribute to combinatorial control. What are they?

DNA methylation usually inhibits transcription. One or more repressor proteins may be involved in the transcriptional regulation. One or more activator proteins may be involved in transcriptional regulation.

Regulator elements are best defined as:

DNA segments that regulate eukaryotic genes

Cell _______ is the process by which cells become specialized into particular types.

Differentiation

True or false: Methylation of DNA near the promoter of a eukaryotic gene activates the transcription of the gene.

False

When and where might alternatively spliced gene products occur?

In different tissues in an animal During different stages in animal development.

How does allolactose affect the lac repressor protein?

It binds to the repressor protein and prevents it from binding to the operator site of the lac operon.

What is the function of DNA methyltransferase?

It methylates DNA

Match the structural gene in the lac operon with the enzyme it produces.

LacZ - B-galactosidase LacY - Premease LacA - Transacetylase

The genes found in the lac operon of E. coli are used for the metabolism of ___________ .

Lactose

How can DNA methylation inhibit transcription?

Methylation can prevent an activator from binding to an enhancer. Methylation can alter chromatin structure.

_______ control is a form of transcription in which a repressor protein decreases the rate of transcription.

Negative.

_____ control is transcriptional regulation by activator proteins.

Positive

The lac repressor protein pevents the enzyme _____ _________ from transcribing the genes in the lac operon.

RNA polymerase

What are silencers?

Regulatory elements that can prevent or decrease transcription.

Match the type of transcription factor with the proper form of transcriptional regulation.

Repressor - negative control Activator - positive control Regulatory transcription factors - both positive and negative control

What is the role of repressor proteins in the regulation of transcription?

Repressor proteins bind to DNA and decrease the rate of transcription.

_______ are regulatory transcription factors that bind to DNA and decrease the rate of transcription.

Repressors

Which of the following are proteins involved in regulating the rate of transcription in eukaryotes?

Repressors Activators

When are the genes involved in lactose metabolism in E. coli expressed and when are they turned off?

The genes for lactose metabolism are expressed when lactose is present but not when it is absent.

Small effector molecules bind to a regulatory __________ factors and cause confrontational changes that influence their ability to bind to DNA

Transcription

Eukaryotes can regulate gene expression in several ways. Match each level of regulation with the correct description.

Transcription - Control of synthesis of mRNA from a gene RNA processing - Regulation of splicing of mRNA Translation - Regulation of protein synthesis Post translation - Regulation of the amount or function of a protein that has already been synthesized

When the sugar _______ binds to the repressor protein, this causes a conformational change that prevents the repressor from binding to the _______ site.

allolactose, operator

How does cAMP play a role in the transcription of the lac operon.

cAMP binds to CAP and together they bind to the DNA, which enhances transcription of the lac operon.

When ____ binds to CAP, the resulting complex binds to the CAP site near the lac _________. This causes a bend in the DNA that enhances the ability of RNA polymerase to bind, and so the transcription rate is increased.

cAMP, promoter

When a chromatin is tightly packed, this is called the _________ conformation, and when it is loosely packed, this is called the ______ conformation.

closed; open

Genes that have relatively constant levels of expression in all conditions over time are said to be ________ genes.

constitutive

When a gene is expressed constantly over time in a cell, it is a(n):

constitutive gene

The small effector molecule that is involved in the activation of the lac operon in the absence of glucose is __________ .

cyclic AMP

During mammalian development

different globin genes are expressed at different developmental stages

In eukaryotic DNA, regulatory elements known as _______ play a role in the ability of RNA polymerase to begin transcription, thereby increasing the rate of transcription.

enhancers

The morphologies of different cell types, such as skin cells and nerve cells, is strikingly different. This is due to the fact that the cells:

express different genes

The production of the functional product of a gene is called

gene expression.

Covalent modifications to _______ proteins can affect gene expression by activating or silencing the transcription of genes.

histone

The acetylation of ____________ proteins can loosen chromatin packing.

histone

The _______ ________ hypothesis states that covalent modifications of histones are a language directing interactions between histones and chromatin.

histone code

A small effector molecule that increases the rate of transcription is called a(n) ________ .

inducer

Match each component of the lac operon with the correct description.

lacZ - Gene that encodes B-galactosidase lacY - Gene that encodes lactose permease lacA - Gene that encodes galactose transacetylase lacO - regulatory sequence that provides a binding site for a repressor protein lacP - Promoter for the lac operon genes CAP site - regulatory sequence that is recognized by an activator protein

Which of the following genes encodes the lac repressor protein?

lacl

Eukaryotes, but not prokaryotes, can regulate gene expression at the level of:

mRNA processing

In E. coli, the genes required to metabolize lactose are expressed:

only when lactose is present

In the lac operon, the ________ is the DNA sequence at which the lac repressor binds.

operator

An mRNA that encodes more than one protein is called ________ mRNA.

polycistronic

The catabolite activator protein (CAP) is involved in _______ control of the lac operon.

positive

Regulatory transcription factors influence the expression of genes by binding directly to DNA at or near the _______ site and affect the rate of transcription.

promoter

What are the basic components of the lac operon?

promoter lacA lacZ lacY

Gene ________ is the ability of cells to control the expression of genes.

regulation

The transcription of the lac operon genes is inhibited when the lac repressor protein binds to

the lac operator

According to the histone code hypothesis, proteins recognize histones based on

their covalent modifications

In both prokaryotes and eukaryotes, most gene regulation occurs when cells regulate the level of ____________ of a gene.

transcription

What is the order of the steps that activator proteins take in order to promote the unraveling of compact chromatin at the site of gene transcription?

1. Transctiptional activator binds to an open enhancer site. 2. Activators recruit chromatin remodeling proteins. 3. Compacted chromatin is loosened 4. Transcription occurs

How does the presence of lactose in the cell influence the transcription of the lac operon?

1. When lactose is present, transcription of the lac operon is high. 2. When lactose is present, the lac repressor protein does not bind to the operator site and transcription can occur.

What is the organization of the genes in the lac operon, starting from the lac regulatory gene (lacl) and ending with the lac terminator? Place the DNA element nearest to lacl on top.

1. lacP (promoter) 2. lacO (operator) 3. lacZ 4. lacY 5 lacA

The lac operon is also under positive control by an activator protein called what?

CAP

When cAMP binds to a protein called _____, it enhances the transcription of the genes of the lac operon.

CAP

An activator protein recognizes the _______ of the lac operon.

CAP site

Which of the following are key differences between eukaryotic and prokaryotic transcriptional regulation?

Combinatorial control of gene expression is more common in eukaryotes. The majority of genes are organized individually in eukaryotes, but are organized as operons in prokaryotes The complexity of eukaryotic development requires that transcription be more coordinated and integrated than in prokaryotes.

Which of the following form the pre-initiation complex, including the binding site?

GTFs RNA polymerase TATA box

What is the process by which a cell controls the level of expression of a specific gene or set of genes in a biological pathway?

Gene regulation

In order to initiate transcription, RNA polymerase II must associate with proteins known as ________ transcription factors at the TATA box of the core promoter.

General

A cell's total DNA compliment is called its

Genome

Match each mechanism for the regulation of gene expression with the proper description.

Negative control - A repressor protein binds to DNA and blocks transcription. Positive control - An activator protein binds to DNA and activates transcription. Induction - A small effector molecule activates transcription. Repression - A small effector molecule prevents transcription.

A(n) __________ is a cluster of genes that are part of a single transcription unit that is under the control of a single promoter.

Operon

At what level does gene regulation occur in prokaryotes?

Post-translation Transcription Translation

The ________ is the collection of all proteins that are expressed in a cell.

Proteome

How is the regulation of transcription similar in eukaryotes and prokaryotes?

Small effector molecules are involved in gene regulation proteins influence the ability of RNA polymerase to bind to the DNA

How does glucose repress the expression of the lac operon?

Glucose inhibits the production of cAMP, thereby preventing the activation of the lac operon.

Transcription of the lac operon will be highest when ________ is absent and _______ is present.

Glucose; Lactose

Under which environmental conditions is the lac operon "turned off" or it has very low levels of transcription?

High lactose and High glucose Low lactose and High glucose Low lactose and Low glucose

How can gene regulation be specific?

Specific genes are expressed at different developmental stages. Specific genes differ in expression levels from cell to cell. Specific genes are expressed only in certain cells.

What are the two components of the core promoter?

TATA box transcriptional start site

Which of the following describe the TATA box? Choose all that apply.

The TATA box is a sequence upstream of the transcriptional start site. The TATA box determines the precise starting point for transcription.

What are two major benefits of gene regulation?

The conservation of energy expression of genes at appropriate times