Gene regulation

Question 1

Operon

Answer 1

A block where structural proteins with related functions are usually encoded together within the genome

Question 2

Type I Topoisomerases

Answer 2

• Create single stranded cuts in DNA

- No ATP require

Question 3

Type II Topoisomerases

Answer 3

• Create double stranded break

- Require ATP

Question 4

Polycistronic

Answer 4

code more than one protein

Question 5

Monocistronic

Answer 5

code one protein

Question 6

What regulate transcription

Answer 6

Sigma factor

Question 7

What is sigma factor

Answer 7

Subunit of the RNA polymerase complex that recognizes the specific promoter sequence of DNA that the RNA polymerase complex should bind to

Question 8

What activator regulator do?

Answer 8

Bind to specific DNA binding site and increase transcription

Question 9

What repressor regulator do?

Answer 9

Bind to operator and reduce transcription

Question 10

Operator

Answer 10

A short region of DNA lies partially within the promoter and interacts with regulatory protein controlling transcription of operon

Question 11

Catabolite repression

Answer 11

Process which biphasic growth in glucose lactose environment involves

Question 12

What catabolite repression do?

Answer 12

Allow microorganism to adapt quickly to preferred carbon and energy source first

Question 13

Lac operon

Answer 13

Well-characterized, tightly regulated operon

Question 14

Inducible

Answer 14

Being able to turn on or off by specific small molecules

Question 15

Why lac operon is important?

Answer 15

• Require for transport and metabolism of lactose

- Allow effective digestion of lactose when glucose is not available through the activity of beta-galactosidase

Question 16

Characteristics of lac operon

Answer 16

• Inducible

- Positively (when glucose is not present) and negatively regulated

Question 17

Negative lac operon

Lactose is absent

Answer 17

1. lacI code mRNA which going into protein
2. Protein active and combine into operator and block access of RNA polymerase
3. Since RNA polymerase cannot go into, no RNA transcription made

Question 18

Negative lac operon

Lactose is present

Answer 18

1. Inducer Allolactose bind to protein and inhibit that repressor
2. RNA transcription is on

Question 19

Positive lac operon

Glucose is absent

Answer 19

1. Induccer cAMP activate CAP
2. CAP bind to binding site that enhance the binding of RNA polymerase to promoter
3. Upregulation of transcription

Question 20

Positive lac operon

Glucose is present

Answer 20

If CAP is not active, RNA polymerase still bind to promoter but not effectively

Question 21

What is attenuation?

Answer 21

Mechanism based on coupling of transcription and translation to prevent completion of transcription

Question 22

trp operon

Tryptophan is absent

Answer 22

1. Inactive repressor protein cannot bind to operator

2. Operon on

Question 23

trp operon

Tryptophan is present

Answer 23

1. Tryptophan activate repressor protein and make it bind to operator
2. Operon off, no RNA made

Question 24

Attenuation

High level of trytophan

Answer 24

1. Ribosome add tryptophan to peptide chain and move along with transcript
2. Ribosome block interaction between region 1 and 2
3. Region 3 and 4 form hair loop and pull RNA polymerase off the transcript

Question 25

Attenuation

Low level of trytophan

Answer 25

1. Ribosome add tryptophan to peptide chain but cannot move along with transcript as well as protect region 2
2. Region 2 and 3 interact and form stem loop
3. RNA polymerase will not be pulled out