Chapter 14

Question 1

The collection of all proteins that are expressed in a cell is known as the

Answer 1

proteome

Question 2

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

Answer 2

express different genes

Question 3

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?

Answer 3

Gene regulation

Question 4

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

Answer 4

constitutive gene

Question 5

Multicellular organisms ensure that most proteins are produced at appropriate times and in appropriate cell types via the regulation of the ______that encode these proteins.

Answer 5

genes

Question 6

The complete set of genes present in a cell is called its

Answer 6

Genome

Question 7

The different cell types of an individual carry the same set of genes, and so contain the same _______.However, the collection of proteins they make, or ______, is quite different.

Answer 7

Genome - Proteome

Question 8

The ability of cells to control the expression of genes is termed gene ____

Answer 8

regulation

Question 9

Which of the following is an example of developmental gene regulation in mammals?

Answer 9

Different globin genes are expressed in the embryo, fetus, and adult.

Question 10

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

Answer 10

constitutive

Question 11

What are two major benefits of gene regulation?

Answer 11

Expression of genes at appropriate times

The conservation of energy

Question 12

During development in mammals,

Answer 12

different globin genes are expressed at different developmental stages

Question 13

How do the mammalian embryo and fetus acquire oxygen from the mother’s bloodstream?

Answer 13

The embryo and fetus remove oxygen from the mother’s blood stream due to the high binding affinity of hemoglobin made during development.

Question 14

At what levels does gene regulation occur in bacteria?

Answer 14

Post-translation

Transcription

Translation

Question 15

Which of the following are ways of regulating gene expression in BOTH prokaryotes and eukaryotes?

Answer 15

Post-translational regulation

Regulation of transcription

Regulation of translation

Question 16

When geneticists say a gene is “turned on,” they mean that it is _______ into mRNA.

Answer 16

transcribed

Question 17

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

Answer 17

mRNA processing

Question 18

Regulation of bacterial gene expression typically involves all of the following mechanisms except

Answer 18

regulation of RNA processing

Question 19

When is a gene “turned off”?

Answer 19

When very little or no mRNA is transcribed from the gene

Question 20

Match each regulated step of eukaryotic gene expression with the appropriate description.
Transcription
RNA processing
Translation
Post-translation

Answer 20

Transcription - The amount of RNA synthesized from a gene is regulated.
RNA processing - Two or more different types of mRNA are created from a single gene.
Translation - The amount of protein synthesized from a mRNA is regulated.
Post-translation - Protein function is affected by feedback inhibition, covalent modifications, and degradation.

Question 21

How does gene regulation differ between prokaryotes and eukaryotes?

Answer 21

Eukaryotes process mRNA transcripts in ways that prokaryotes do not.

Question 22

At what levels does gene regulation occur in eukaryotes?

Answer 22

Transcription

Translation

Processing of mRNA

Post-translation

Question 23

What are regulatory transcription factors?

Answer 23

Proteins that bind to DNA and affect the transcription of one or more genes

Question 24

When transcription is regulated by repressor proteins, this is called _____ control

Answer 24

negative

Question 25

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

Answer 25

They bind to DNA and decrease the rate of transcription.

Question 26

Transcriptional regulation by activator proteins is a type of regulation called _____ control

Answer 26

positive

Question 27

Regulatory transcription factors influence the expression of genes by affecting the rate of transcription. They do so by binding directly to DNA at or near the_____ site

Answer 27

promoter

Question 28

Regulatory transcription factors that bind to the DNA and decrease the rate of transcription are called ______. This is a form of regulation called______control. On the other hand, factors that bind to the DNA and increase the rate of transcription are termed_______.These engage in a form of regulation known as ______ control

Answer 28

1. repressor 2. negative 3. activator 4. positive

Question 29

What is the role of small effector molecules in transcriptional control?

Answer 29

They bind to transcription regulatory factors and alter how they bind to DNA.

Question 30

What is an operon?

Answer 30

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

Question 31

Polycistronic mRNA

Answer 31

encodes more than one protein

Question 32

What are the basic components of the lac operon?

Answer 32

lacZ Promoter lacA lacY

Question 33

Small effector molecules bind to certain proteins and cause conformational changes that influence the ability of these proteins to bind to DNA. Such proteins are called regulatory_____factors

Answer 33

transcription

Question 34

Match each protein expressed by the lac operon and its function in the breakdown of lactose. β-galactosidase Lactose permease Galactoside transacetylase

Answer 34

β-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

Question 35

In the lac operon, the operator is

Answer 35

the DNA sequence at which the lac repressor binds

Question 36

What does the lac operon region contain?

Answer 36

Promoter, operator, and three structural genes

Question 37

What are the three major functions of the enzymes encoded by the lac operon?

Answer 37

The transport of lactose across the cell membrane The modification of lactose and lactose analogues The breakdown of lactose

Question 38

Which of the following genes encodes the lac repressor protein?

Answer 38

lacI

Question 38

An activator protein recognizes the ___________ of the lac operon.

Answer 38

CAP site

Question 39

How does allolactose affect the lac repressor protein?

Answer 39

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

Question 40

What is an inducer?

Answer 40

A small effector molecule that increases the rate of transcription

Question 41

Why is the lac operon considered inducible?

Answer 41

When allolactose is produced, this causes the transcription of the lac operon.

Question 42

A conformational change in the lac repressor protein occurs upon binding of the sugar _______ to it. This change in shape prevents the repressor from binding to the _____- site.

Answer 42

allolactose - operator

Question 43

A ______-effect is mediated by a DNA element that binds regulator proteins, whereas a ______-effect is mediated by genes that encode diffusible regulatory proteins.

Answer 43

cis; trans

Question 44

A DNA segment that must be adjacent to the gene that it regulates is known as a(n) ____-____ element.

Answer 44

cis-acting

Question 45

The small effector molecule that is involved in the positive control of the lac operon is

Answer 45

cyclic AMP

Question 46

How do CAP and cAMP increase the transcription of the lac operon?

Answer 46

When CAP and cAMP bind to the CAP site, this enhances binding of RNA polymerase to the promoter site.

Question 47

When glucose is present in a bacterial cell, it can act to repress the expression of the lac operon because it is preferentially used compared to other sugars. What form of transcriptional regulation is this?

Answer 47

Catabolite repression

Question 48

Of the four possible environments E. coli could encounter with regard to lactose and glucose, which has the highest levels of lac operon transcription?

Answer 48

Low glucose and high lactose

Question 49

What is the role of the corepressor in the expression of the trp operon?

Answer 49

The corepressor binds to the repressor protein and causes a conformational change, which allows the repressor to bind to the operator site.

Question 49

The genes in the trp operon code for enzymes that make the amino acid

Answer 49

tryptophan

Question 50

The binding of the corepressor to the trp repressor results in what?

Answer 50

The repressor binds to the operator and prevents transcription.

Question 51

What is a corepressor molecule?

Answer 51

A small effector molecule that binds to a repressor protein

Question 52

How do the roles of small effector molecules in the lac and trp operons differ?

Answer 52

The trp repressor requires the presence of the small effector molecule to bind to the operator, while the lac repressor does not.

Question 53

What is a repressible operon?

Answer 53

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

Question 54

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

Answer 54

Binding of an activator protein to DNA Loosening of chromatin structure

Question 55

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

Answer 55

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

Question 56

What are the three features common to most promoters that are needed for the initiation of transcription of protein coding genes in eukaryotes?

Answer 56

TATA box Transcriptional start site Regulatory elements

Question 57

What is basal transcription?

Answer 57

The low level of transcription activated by the core promoter alone

Question 58

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

Answer 58

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

Question 58

What is the role of the TATA box?

Answer 58

The TATA box determines the starting point of transcription.