MOD 6: Regulation of Expressions in Prokaryotes

Question 1

TRUE OR FALSE: Prokaryotic cells are generally larger than eukaryotic cells

Answer 1

FALSE; They are smaller

Question 2

TRUE OR FALSE: Eukaryotic cells are round because they do not have cell walls

Answer 2

TRUE

Question 3

What do you call the enzyme that deteriorates cell walls?

Answer 3

Cellulase

Question 4

What factors affect the occurrence of transcription?

Answer 4

1. Environment
2. Cellular activities
   
   • Replication
   • Recombination
   • Repair of DNA
   • Cell division

Question 5

This type of enzyme can be induced and it requires specific factors for it to do its job

Answer 5

Inducible enzyme

Question 6

This type of enzyme is always functioning

Answer 6

Constitutive enzyme

Question 7

This type of enzyme binds to the operator and tells it to stop working. It is produced by a repressor gene

Answer 7

Repressible enzyme

Question 8

Genetic expression occurs unless it is shut off by a regulator molecule. What control is this?

Answer 8

Negative control

Question 9

Transcription occurs only if a regulator molecule directly stimulates RNA production

Answer 9

Positive control

Question 10

These refer to the genes coding for the primary structure of an enzyme

Answer 10

Structural genes

Question 11

What are the three structural genes in the lac operon?

Answer 11

1. lacZ (B-galactosidase)
2. lacY (permease)
3. lacA (transacetylase)

Question 12

TRUE OR FALSE: Bacterial DNA have introns as well

Answer 12

FALSE; They do not

Question 13

TRUE OR FALSE: Proteins are products of genes that will be operons

Answer 13

FALSE; Operons are products of genes that will be proteins

Question 14

Lactose related genes are expressed when lactose is __________ and repressed when __________

Answer 14

Present; absent

Question 15

These are genes that code for similar functions. They tend to be organized in clusters

Answer 15

Operons

Question 16

This type of operon is affected by the presence of lactose

Answer 16

Lac operon

Question 17

Which two scientists discovered the genetic regulatory mechanism, regulation of transcription, and obtain the 1965 Nobel Prize in Medicine?

Answer 17

Francois Jacob and Jacques Monod (Jacob Monod Lac Operon)

Question 18

With lactose, the disaccharide is broken down into 2 monosaccharides. What are they?

Answer 18

Glucose and galactose

Question 19

Lac operon produces an enzyme to break down lactose. What is this enzyme?

Answer 19

B-galactosidase

Question 20

What are the two binding sites of the repressor protein?

Answer 20

Operator gene and lactose

Question 21

What process does the repressor protein block?

Answer 21

Transcription

Question 22

With the absence of lactose, it is repressed. Where does the repressor protein bind to?

Answer 22

It binds to the operator gene

Question 23

With the presence of the repressor protein, its conformation is changed. Where does the repressor protein bind to?

Answer 23

It binds with the lactose

Question 24

TRUE OR FALSE: The repressor protein can bind to the operator region with or without the presence of lactose.

Answer 24

FALSE; The repressor protein cannot bind to the operator region with the presence of lactose

Question 25

Which does a cell prefer, lactose or glucose? What happens to the other?

Answer 25

The cell prefers glucose for glycolysis. Lactose then shuts down.

Question 26

What type of control does the catabolite-activating protein (CAP) exert over the lac operon?

Answer 26

Positive control

Question 27

What is the condition of glucose and lactose when: - cAMP levels increase - cAMP forms complex with cAP - binds with cAP-binding site - transcription and translation - structural genes are expressed

Answer 27

Without glucose, with lactose

Question 28

What is the condition of glucose and lactose when: - cAMP levels decrease - cAMP does not form complex with cAP - no binding with cAP-binding site - glucose cannot bind efficiently - translation is diminished

Answer 28

With glucose, with lactose

Question 29

TRUE OR FALSE: Lactose metabolism requires fewer steps and less energy compared to glucose metabolism.

Answer 29

FALSE; By using glucose first the cell maximizes energy efficiency

Question 30

TRUE OR FALSE: The cell avoids unnecessary production of enzymes involved in lactose metabolism when glucose, a more readily metabolizable sugar, is available.

Answer 30

TRUE

Question 31

TRUE OR FALSE: The CAP-cAMP system ensures that the lac operon is only fully activated when glucose levels are low and lactose is present.

Answer 31

TRUE

Question 32

What happens to the repressor with the presence of tryptophan?

Answer 32

Tryptophan binds to the repressor, activating it

Question 33

TRUE OR FALSE: Tryptophan is produced in the cell and cannot be obtained from the environment.

Answer 33

TRUE

Question 34

TRUE OR FALSE: The DNA plays diverse roles in regulation gene expression in bacteria.

Answer 34

FALSE; RNA

Question 35

What are the three types of regulation that fine-tune levels of gene expression in bacteria?

Answer 35

1. Attenuation 2. Riboswitches 3. Small noncoding RNAs (sRNA)

Question 36

TRUE OR FALSE: DNA —> Transcribed to __________ —> decides if it will be converted to __________ or not

Answer 36

mRNA; protein

Question 37

Which groups of scientist discovered attenuation?

Answer 37

Charles Yanofsky, Kevin Bertrand, and their colleagues

Question 38

What is the condition of tRNA when: - tRNA is uncharged - transcription is slow - 1-3 stem-loop is formed

Answer 38

tRNA is unavailable

Question 39

What is the condition of tRNA when: - tRNA is charged - 1, 2, and 3 are separated - 4 forms a loop - termination hairpin is formed

Answer 39

tRNA is available

Question 40

What is the condition of tryptophan levels when: - ribosome translates slowly - antiterminator is formed

Answer 40

Low tryptophan level

Question 41

What is the condition of tryptophan levels when: - ribosome translates quickly - terminator hairpin and associated hairpin are formed

Answer 41

High tryptophan levels

Question 42

This hairpin prevents the formation of the terminator and allows transcription to continue

Answer 42

Antiterminator (Non-terminating hairpin)

Question 43

This begins at the ligand-binding site of the RNA

Answer 43

Riboswitches

Question 44

Riboswitches involve short ribonucleotide sequences present in the __________ of __________

Answer 44

5’-untranslated regions; mRNAs

Question 45

TRUE OR FALSE: The terminator conformation of riboswitches interfaces directly with the transcriptional machinery and shuts it down

Answer 45

TRUE

Question 46

These play regulatory roles in bacteria

Answer 46

Small noncoding RNAs (sRNA)

Question 47

These are involved in gene regulation and the modification of protein function

Answer 47

sRNAs

Question 48

These are transcribed from the opposite strand of DNA and in the opposite direction, making them complementary to mRNAs transcribed from that locus

Answer 48

sRNA

Question 49

Positive or negative regulation? - sRNA binds to the ribosome binding site - no translation

Answer 49

Negative regulation

Question 50

Positive or negative regulation? - ribosome binding site is now open for attachment of the ribosome - translation proceeds, as RBS is unmasked

Answer 50

Positive regulation

Question 51

CRISPR-Cas is an __________ in bacteria

Answer 51

Adaptive Immune System

Question 52

CRISPR-Cas is an __________ in bacteria

Answer 52

Adaptive Immune System

Question 53

Who first discovered nucleotide excision repair in 1964?

Answer 53

Paul Howard-Flandres

Question 54

Who discovered attenuation?

Answer 54

Charles Yanofsky and Kevin Bertrand