2.9 Structure And Control Of Gene Exp. Prokaryotes

Question 1

Function of beta-galactosidase (coded by lac z)

Answer 1

hydrolyses lactose into glucose and galactose

Question 2

Function of lactose permease (coded by lac y)

Answer 2

transports lactose across the cell surface membrane

Question 3

Function of lactose transacetylase (coded by lac a)

Answer 3

involves in the metabolism of lactose, but exact function is unknown

Question 4

What is the basic unit of gene expression in prokaryotes?

Answer 4

Operon

Question 5

True or False: Prokaryotic genes are typically organized in clusters known as operons.

Answer 5

True

Question 6

Fill in the blank: The __________ is the DNA sequence where RNA polymerase binds to initiate transcription.

Answer 6

promoter

Question 7

What is the role of the operator in an operon?

Answer 7

It acts as a regulatory sequence that can inhibit or promote transcription.

Question 8

Multiple Choice: Which component is NOT part of an operon? A. Regulatory Gene B. Promoter C. Structural Genes D. Operator

Answer 8

A. Regulatory Gene

Question 9

What are the 3 main ways of control for the transcription of an operon?

Answer 9

Inducible, Repressive, Activator Control

Question 10

True or False: In prokaryotes, the presence of a active repressor protein prevents transcription.

Answer 10

True

Question 11

Are Enhancers present in prokaryotes?

Answer 11

Enhancers are not present in prokaryotes; they are primarily found in eukaryotic cells.

Question 12

Fill in the blank: The __________ is a protein that binds to the operator to block RNA polymerase from transcribing the gene.

Answer 12

repressor

Question 13

What is the function of an inducer in the context of gene expression?

Answer 13

An inducer binds to a repressor, preventing it from blocking transcription.

Question 14

Multiple Choice: Which of the following is an example of a inducible operon? (inducer can switch operon on!)

Answer 14

Lac operon

Question 15

Short Answer: What does the lac operon regulate?

Answer 15

The metabolism of lactose in E. coli

Question 16

True or False: Prokaryotic transcription and translation occur simultaneously.

Answer 16

True

Question 17

Fill in the blank: The __________ is a sequence in DNA that signals the end of transcription. (in bacteria!)

Answer 17

terminator

Question 18

What is the role of the CAP protein in the lac operon?

Answer 18

CAP enhances the binding of RNA polymerase to the promoter when glucose levels are low.

Question 19

Multiple Choice: Which of the following is NOT a feature of prokaryotic gene expression?

Answer 19

Introns

Question 20

What is the impact of glucose on the lac operon?

Answer 20

High glucose levels reduce the expression of the lac operon to a basal level.

Question 21

True or False: All prokaryotic genes are expressed at all times.

Answer 21

False

Question 22

Fill in the blank: The __________ model describes how the lac operon is regulated by the presence or absence of lactose.

Answer 22

inducible

Question 23

What is a co-repressor?

Answer 23

A small molecule that binds to a repressor protein to activate it, inhibiting transcription.

Question 24

Multiple Choice: Which of the following processes is responsible for producing mRNA in prokaryotes?

Answer 24

Transcription

Question 25

Short Answer: What is the primary enzyme involved in prokaryotic transcription?

Answer 25

RNA polymerase

Question 26

True or False: Prokaryotic genes can be regulated by environmental signals.

Answer 26

True

Question 27

Fill in the blank: The __________ is a segment of DNA that is transcribed into RNA but not translated into protein.

Answer 27

non-coding region

Question 28

What is the primary difference between repressible and inducible operons?

Answer 28

Repressible operons are usually on and can be turned off, while inducible operons are usually off and can be turned on.

Question 29

Multiple Choice: Which of the following is an example of a repressible operon?

Answer 29

Trp operon

Question 30

Short Answer: What does the trp operon regulate?

Answer 30

The synthesis of tryptophan in bacteria.

Question 31

True or False: The presence of tryptophan activates the trp operon.

Answer 31

False

Question 32

Fill in the blank: The __________ region of an operon contains the genes that are co-regulated.

Answer 32

structural

Question 33

What determines the timing of gene expression in prokaryotes?

Answer 33

Environmental conditions and cellular needs.

Question 34

Multiple Choice: Which of the following statements about prokaryotic gene expression is true?

Answer 34

It is often regulated at the transcriptional level.

Question 35

Short Answer: How do prokaryotes respond to changes in nutrient availability?

Answer 35

By regulating gene expression through operons.

Question 36

What does CAP protein stand for? (regulate lac operon)

Answer 36

Catabolite Activator Protein

Question 37

Outcome of Active/Inactive Activator Protein?

Answer 37

ACTIVE Activator Protein => Transcription is at HIGH RATE. INACTIVE Activator Protein => Transcription is at LOW RATE. (Sometimes, the rate is slow enough to be considered negligible / OFF)

Question 38

Structural genes of trp operon?

Answer 38

trpE, trpD, trpC, trpB, trpA

Question 39

What is a polycistronic mRNA

Answer 39

Polycistronic mRNA is a type of mRNA molecule, common in prokaryotes, that encodes multiple proteins, rather than just one, and is transcribed from a single promoter and terminator

Question 40

What regulatory gene codes for the regulatory protein for both lac and trp operon?

Answer 40

trp: trpR, lac: lacl

Question 41

Lac and trp operon's control system and the co-repressor or inducer molecule?

Answer 41

Lac: Inducible, inducer is allolactose Trp: Repressible, co-repressor is tryptophan

Question 42

Significance of Inducible System and Repressible System

Answer 42

Inducible: Ensures that the cell does not synthesize nutrient-metabolizing enzymes until they are needed. Repressible: Ensures that the cell does not waste energy synthesizing unneeded enzymes.