Question 1

What is the name of the linkage than holds the lactose disaccharide together?
A)$\alpha$-galactoside linkage
B)$\beta$-lipophilic linkage
C)$\beta$-glycosidic linkage
D)$\beta$-galactoside linkage
E)ester linkage

Accepted Answer

The linkage that holds the lactose disaccharide together is the β-glycosidic linkage, which connects the galactose and glucose monomers through a β-anomeric carbon. Option A, B, and E are not correct descriptions of this linkage.

Question 2

What is probably the single most important distinction between prokaryotes and eukaryotes?
A)the existence of the Golgi complex
B)the separation of the cell's genetic material from the surrounding cytoplasm
C)the existence of ribosomes
D)the centrioles
E)the lysosomes and peroxisomes

Accepted Answer

The separation of the cell's genetic material from the surrounding cytoplasm is the most significant difference between prokaryotes and eukaryotes. Prokaryotes do not have a nucleus or other membrane-bound organelles, whereas eukaryotes do. This separation allows for more complex cellular processes and genetic regulation in eukaryotes.

Question 3

What is the name of the proteins that make up the nuclear lamina and of what protein superfamily are they a member?
A)lamins,laminins
B)lamins,intermediate filaments
C)keratin,intermediate filaments
D)keratin,laminins
E)actin,microfilaments

Accepted Answer

The nuclear lamina is made up of proteins called lamins, which are members of the intermediate filament protein superfamily.

Question 4

With what structure is the outer membrane of the nuclear envelope continuous?
A)RER
B)SER
C)Golgi complex
D)the spindle
E)the plasma membrane

Accepted Answer

The outer membrane of the nuclear envelope is continuous with the rough endoplasmic reticulum (RER). This is because the RER is studded with ribosomes that are involved in protein synthesis, and proteins that are destined for the nucleus are synthesized on the RER and transported to the nucleus through the nuclear pores. The smooth endoplasmic reticulum (SER) is involved in lipid metabolism and detoxification, and is not directly connected to the nuclear envelope. The Golgi complex is involved in modification and sorting of proteins, and is also not directly connected to the nuclear envelope. The spindle is involved in cell division, and is not part of the nuclear envelope. The plasma membrane is the outermost membrane of the cell, and is not connected to the nuclear envelope.

Question 5

The type of control exercised if the interaction of a regulatory protein and DNA inhibits transcription.
A)positive control
B)negative control
C)averaged control
D)circumspect control
E)neutral control

Accepted Answer

Negative control occurs when a regulatory protein inhibits transcription by blocking RNA polymerase from binding to the promoter region of DNA. This results in a decrease or complete inhibition of gene expression. Therefore, option B, negative control is the correct answer.

Question 6

Which of the traits below is characteristic of the classical nuclear localization signals?
A)possession of large numbers of hydrophobic amino acids
B)possession of one or two short stretches of negatively charged amino acids
C)possession of one or two short stretches of positively charged amino acids
D)twisted backbones
E)double helical regions

Accepted Answer

The classical nuclear localization signals typically possess one or two short stretches of positively charged amino acids, such as lysine or arginine. These positively charged residues interact with negatively charged molecules in the nuclear pore complex to facilitate transport into the nucleus.

Question 7

The thin filamentous meshwork within the nucleus that is bound by integral membrane proteins of the inner surface of the nuclear envelope in animal cells is called the _________.
A)basement lamina
B)basal lamina
C)nuclear lamina
D)nucleon
E)nuclear limulus

Accepted Answer

The nuclear lamina is a thin filamentous meshwork within the nucleus of animal cells that is bound by integral membrane proteins of the inner surface of the nuclear envelope. The basement lamina and basal lamina are extracellular matrices found outside of the cell, and nucleon and nuclear limulus are not correct terms for this structure.

Question 8

To what is the NLS - protein cargo - importing $\alpha$/$\beta$ complex thought to bind when it seems to dock to the outer surface of the nucleus near the nuclear pore complex?
A)the torus
B)the outer ring of the nuclear pore complex
C)the inner ring of the nuclear pore complex
D)cytoplasmic filaments that extend from the outer ring of the nuclear pore complex
E)the transporter

Accepted Answer

The complex is thought to bind to cytoplasmic filaments that extend from the outer ring of the nuclear pore complex, which helps guide it towards the nuclear pore.

Question 9

What site on a bacterial operon segment of a chromosome is adjacent to or overlaps with a promoter?
A)operator
B)terminator
C)activator
D)repressor
E)structural genes

Accepted Answer

The operator site on a bacterial operon segment of a chromosome is located adjacent to or overlaps with the promoter site. The operator site is where the repressor protein binds to prevent transcription of the downstream structural genes.

Question 10

A transport receptor that moves macromolecules from the cytoplasm to the nucleus is called a(n)____.
A)exhalin
B)exportin
C)importin
D)transportin
E)receptin

Accepted Answer

The transport receptor that moves macromolecules from the cytoplasm to the nucleus is called importin. Exportin, transportin, exhalin, and receptin are not involved in nuclear import.

Question 11

The operator __________.
A)is the site on the DNA where the repressor binds
B)is the site on the DNA where DNA polymerase binds
C)is the site on the DNA where reverse transcriptase binds
D)is the site on the RNA where the repressor binds
E)is the site on the ribosome where the repressor binds

Accepted Answer

The operator is the site on the DNA where the repressor molecule binds, which controls the expression of genes in prokaryotic and eukaryotic organisms. The binding of repressor to the operator site prevents the binding of RNA polymerase to the promoter region, thereby inhibiting the transcription of genes.

Question 12

Which of the following words or phrases does not accurately describe the contents of the nucleus?
A)viscous
B)amorphous
C)undistinguished morphology
D)crystalline
E)highly extended nucleoprotein

Accepted Answer

The contents of the nucleus do not have a crystalline structure. The other choices are accurate descriptions of the nucleus: A) viscous refers to the consistency of the nucleoplasm, B) amorphous means lacking a defined shape, C) undistinguished morphology refers to the lack of structural features visible under light microscopy, and E) highly extended nucleoprotein describes the molecular composition of the nucleus.

Question 13

What is the name of the site where RNA polymerase binds to the DNA prior to the beginning of transcription?
A)the operator
B)the terminator
C)the promoter
D)the repressor
E)the structural genes

Accepted Answer

The site where RNA polymerase binds to the DNA prior to the beginning of transcription is called the promoter region. This region contains specific sequences of DNA that allow RNA polymerase to recognize and bind to the DNA, ultimately initiating transcription of the gene. The operator, terminator, repressor, and structural genes are all other important components of gene expression, but they are not directly involved in the initiation of transcription by RNA polymerase.

Question 14

$\beta$-galactosidase is encoded by the ___________.
A)y gene of the lac operon
B)z gene of the lac operon
C)a gene of the lac operon
D)y gene of the trp operon
E)z gene of the trp operon

Accepted Answer

The β-galactosidase enzyme is encoded by the z gene of the lac operon in E. coli.

Question 15

Which of the following is not included within the nucleus of a typical interphase (nonmitotic)cell?
A)chromosomes
B)nuclear matrix
C)nucleolus
D)nucleoplasm
E)mesosome

Accepted Answer

Mesosomes are not a component of the nucleus. They are invaginations of the plasma membrane found in bacterial cells. The other options (chromosomes, nuclear matrix, nucleolus, nucleoplasm) are all components of the nucleus.

Question 16

What two monosaccharides combine to form lactose?
A)2 glucose molecules
B)glucose and galactose
C)galactose and fructose
D)2 galactose molecules
E)glucose and fructose

Accepted Answer

Lactose is composed of one molecule of glucose and one molecule of galactose.

Question 17

A section of a bacterial chromosome in which genes for the enzymes of a particular metabolic pathway are clustered together in a functional complex under coordinate control is called a(n)______.
A)operator
B)operon
C)promoter
D)repressor
E)activator

Accepted Answer

An operon is a section of bacterial DNA that contains a cluster of genes involved in a specific metabolic pathway, which are controlled by a single promoter and operator. The genes within an operon are transcribed together into a single mRNA molecule, which is then translated into proteins that function together as a functional complex. This coordinated regulation allows bacteria to efficiently control the expression of genes involved in the same process. Operators, promoters, repressors, and activators are all regulatory elements involved in the control of gene expression within operons.

Question 18

The lac operon is an example of a(n)_______ operon.
A)noninducible
B)constitutive
C)inducible
D)repressible
E)irrepressible

Accepted Answer

The lac operon is an inducible operon, as it is only activated in the presence of lactose or other inducers.

Question 19

What is a regulatory protein for a gene? It binds to specific DNA sequences with high affinity and plays a predominant role in determining if a genome segment is transcribed or not.
A)the operator
B)the terminator
C)the promoter
D)the repressor
E)the structural genes

Accepted Answer

The repressor is a regulatory protein that binds to specific DNA sequences, called operators, with high affinity. The binding of a repressor to an operator blocks the binding of RNA polymerase to the promoter, preventing transcription of the structural genes. Therefore, the repressor plays a predominant role in determining if a genome segment is transcribed or not. The operator, terminator, promoter, and structural genes are all involved in the process of transcription, but only the repressor is specifically responsible for regulating transcription by binding to operators.

Question 20

How do allolactose and lactose differ?
A)They are composed of different sugars.
B)Allolactose has a negative charge,while lactose has a positive charge.
C)The type of linkage holding the two constituent sugars together differs between lactose and allolactose.
D)The order of the sugars is reversed in the two molecules.
E)The constituent sugars are both upside down in lactose and right-side-up in allolactose.

Accepted Answer

Allolactose and lactose differ in the type of glycosidic linkage between the glucose and galactose units. In lactose, the linkage is β-1,4-glycosidic, while in allolactose, which is an isomer of lactose, the linkage is β-1,6-glycosidic. This difference in linkage is crucial for the function of allolactose as an inducer of the lac operon in bacteria.

Quiz 12: Control of Gene Expression

What is the name of the linkage than holds the lactose disaccharide together?

What is probably the single most important distinction between prokaryotes and eukaryotes?

What is the name of the proteins that make up the nuclear lamina and of what protein superfamily are they a member?

With what structure is the outer membrane of the nuclear envelope continuous?

The type of control exercised if the interaction of a regulatory protein and DNA inhibits transcription.

Which of the traits below is characteristic of the classical nuclear localization signals?

The thin filamentous meshwork within the nucleus that is bound by integral membrane proteins of the inner surface of the nuclear envelope in animal cells is called the _________.

To what is the NLS - protein cargo - importing $\alpha$ / $\beta$ complex thought to bind when it seems to dock to the outer surface of the nucleus near the nuclear pore complex?

What site on a bacterial operon segment of a chromosome is adjacent to or overlaps with a promoter?

A transport receptor that moves macromolecules from the cytoplasm to the nucleus is called a(n) ____.

The operator __________.

Which of the following words or phrases does not accurately describe the contents of the nucleus?

What is the name of the site where RNA polymerase binds to the DNA prior to the beginning of transcription?

$\beta$ -galactosidase is encoded by the ___________.

Which of the following is not included within the nucleus of a typical interphase (nonmitotic) cell?

What two monosaccharides combine to form lactose?

A section of a bacterial chromosome in which genes for the enzymes of a particular metabolic pathway are clustered together in a functional complex under coordinate control is called a(n) ______.

The lac operon is an example of a(n) _______ operon.

What is a regulatory protein for a gene? It binds to specific DNA sequences with high affinity and plays a predominant role in determining if a genome segment is transcribed or not.

How do allolactose and lactose differ?