Question 1

So-called two-component regulatory systems

Accepted Answer

Two-component regulatory systems include a sensor kinase and a response regulator, and are involved in regulating various cellular processes such as sporulation in Bacillus and the OmpF and OmpC porin proteins in E. coli. Therefore, choice D is the best answer.

Question 2

If Escherichia coli is cultured in broth containing both glucose and lactose, it

Accepted Answer

E. coli prefers glucose as its primary energy source and will utilize it until the supply is exhausted, then it will switch to lactose. This is due to the fact that the genes for glucose metabolism are constitutively expressed while the genes for lactose metabolism are inducible and only expressed when lactose is present. There is also a phenomenon called catabolite repression where glucose inhibits the expression of the lactose metabolism genes even when lactose is present, which further supports the idea that E. coli will use glucose preferentially.

Question 3

__________ alter repressor proteins thereby increasing the rate of transcription initiation.

Accepted Answer

Inducers are molecules that can bind to repressor proteins and change their shape, preventing them from binding to DNA and thus increasing the rate of transcription initiation.

Question 4

The sensor kinase for the OmpF: OmpC two-component regulatory system is

Accepted Answer

The sensor kinase for the OmpF: OmpC two-component regulatory system is the EnvZ protein. The EnvZ protein detects changes in osmolarity and regulates the expression of the outer membrane porins OmpF and OmpC in response.

Question 5

Bacteria, Archaea, and Eukarya differ in both their genome structure as well as in the steps required to complete gene expression.

Accepted Answer

Bacteria, Archaea, and Eukarya have different genome structures and use different mechanisms to complete gene expression. For example, bacteria and archaea often have circular genomes and use transcription and translation to synthesize proteins, while eukaryotes have linear genomes, undergo RNA processing, and have more complex transcriptional and translational regulation.

Question 6

If a particular end product is already present in abundant amounts in the environment, cells will usually not continue to produce enzymes whose sole purpose is to manufacture more of that end product.

Accepted Answer

This is known as feedback inhibition, where the end product of a metabolic pathway acts as a non-competitive inhibitor of the first enzyme in the pathway, thereby shutting down the pathway and preventing over-accumulation of the end product.

Question 7

Two-component signal transduction systems are found in the Bacteria, but not in Archaea.

Accepted Answer

Two-component signal transduction systems are also found in some Archaea, including halophiles and thermophiles.

Question 8

If a set of genes is repressed in the presence of the controlling substance, it is referred to as __________ control.

Accepted Answer

The answer of If a set of genes is repressed...

Question 9

When there is no arabinose available in the environment, the AraC protein acts as a(n) ______________ for the
E. coli ara operon.

Accepted Answer

The answer of When there is no arabinose available in...

Question 10

______________ is used to control transcription of some anabolic pathways involved in amino acid biosynthesis.

Accepted Answer

Attenuation is a regulatory mechanism used to control transcription of some anabolic pathways involved in amino acid biosynthesis. This mechanism allows the cell to sense the availability of amino acids and adjust the rate of their synthesis in response. Catabolite repression refers to the repression of catabolic pathways when a preferred carbon source is present, while induction refers to the activation of gene expression in response to a specific stimulus or condition. Therefore, neither B nor C is the correct answer.

Question 11

When arabinose is present in the environment, the AraC protein acts as a(n) ______________ for the
E. coli ara operon.

Accepted Answer

The answer of When arabinose is present in the environment,...

Question 12

The real inducer for the
E. coli lac operon is allolactose produced by the action of permease on lactose.

Accepted Answer

The answer of The real inducer for the
E. coli lac...

Question 13

__________ activate repressor proteins thereby decreasing the synthesis of certain enzymes.

Accepted Answer

Corepressors activate repressor proteins, which decrease the synthesis of certain enzymes. Inducers, on the other hand, activate transcription by binding to activator proteins. Effectors and modulators are more general terms that can refer to compounds that affect enzyme activity, gene expression, or other cellular processes.

Question 14

Regulation of gene expression serves to do all of the following except

Accepted Answer

Regulation of gene expression is not aimed at adjusting the activity of existing proteins in the cell. Instead, it is focused on controlling the production of proteins in response to environmental cues and cellular needs. The other options (A, B, and D) are valid reasons for regulating gene expression.

Question 15

The binding of arabinose to the AraC protein allows it to form a loop in the DNA upstream of the ara operon promoter.

Accepted Answer

The answer of The binding of arabinose to the AraC...

Question 16

In two component regulatory systems, the response regulator typically receives a ____________ from the sensor kinase when it has been activated.

Accepted Answer

The response regulator in a two-component regulatory system typically receives a phosphoryl group from the sensor kinase when it has been activated. This phosphorylation event often leads to a conformational change in the response regulator, allowing it to bind to target genes and initiate a cellular response.

Question 17

If a set of genes is induced in the presence of the controlling substance, it is referred to as __________ control.

Accepted Answer

The answer of If a set of genes is induced...

Question 18

In the presence of both glucose and lactose, the lactose repressor is not bound to the operator and the genes of the lactose operon are expressed.

Accepted Answer

In the presence of both glucose and lactose, the lactose repressor can be inactivated by allolactose (a form of lactose), allowing the genes of the lactose operon to be potentially expressed. However, the presence of glucose activates a separate regulatory mechanism that suppresses the expression of these genes by preventing the accumulation of cAMP, which is necessary for the activation of the operon by CAP (catabolite activator protein). Thus, the full expression of the lactose operon in the presence of glucose is inhibited, even if the repressor is not bound to the operator.

Question 19

The

Accepted Answer

The answer of The
...

Question 20

While standard two-component regulatory systems typically act to control gene transcription, phosphorelay systems can act either to control gene transcription or to control

Accepted Answer

Phosphorelay systems can control protein activity by phosphorylating and activating or inactivating target proteins. While they can also regulate gene transcription, this is not the only function of phosphorelay systems. Therefore, option B is the best choice.

Quiz 13: Microbial Genetics Regulation of Gene Expression