modulating transcription

Question 1

what culture medium do prokaryotes grow in (lab wise)

Answer 1

with a culture medium that is stock filled with nutrients, which include amino acids, vitamins, nucleotides, and carbohydrates

Question 2

What role does DNA in the bacterial nucleoid play?

Answer 2

contains all the genetic information required for the cell to respond to environmental changes

Question 3

what are housekeeping genes

Answer 3

genes that are required all the time for normal cellular function & constantly expressed (always transcribed and translated)

• allow for the continuous maintenance of essential cellular activities needed for survival

Question 4

What types of proteins are encoded by housekeeping genes?

Answer 4

encode proteins essential for basic cell function, including:

• Structural proteins
• RNA polymerase and DNA polymerase
• Ribosomal proteins

Question 5

What are regulated genes?

Answer 5

genes that can be turned on or off depending on environmental conditions

Question 6

How do bacteria respond to environmental changes at the genetic level?

Answer 6

they alter the expression patterns of regulated genes, turning specific genes on or off as needed

Question 7

What is the purpose of regulated gene expression in bacteria?

Answer 7

To produce specific enzymes and proteins required for:

• Changes in growth
• Changes in cell division
• Adaptation to new environmental conditions

Question 8

Why are enzymes important for bacterial cells?

Answer 8

they metabolize nutrients, allowing cells to convert macromolecules into usable energy

Question 9

What must cells do with macromolecules like carbohydrates?

Answer 9

break down carbohydrates into usable energy sources, such as ATP

Question 10

What is the preferred energy source for Escherichia coli (E. coli)?

Answer 10

glucose

Question 11

What happens when E. coli runs out of glucose?

Answer 11

Bacterial growth stops (is arrested)

Question 12

How can E. coli survive after glucose is depleted?

Answer 12

E. coli can switch to metabolizing an alternative fuel source, such as lactose, through gene regulation

Question 13

What happens when E. coli is grown in both glucose and lactose?

Answer 13

E. coli will use all available glucose first & then switch to metabolizing lactose

Question 14

What controls the switch between glucose and lactose metabolism?

Answer 14

Products of glucose metabolism

Question 15

When are lactose-metabolizing genes expressed in E. coli?

Answer 15

when glucose is absent and lactose is present

• this produces lactose metabolizing enzymes

Question 16

What happens to bacterial growth when glucose is consumed?

Answer 16

• Growth occurs steadily while glucose is available
• When glucose is depleted → growth temporarily stops
• Growth resumes after switching to lactose metabolism

Question 17

What enzyme is responsible for lactose metabolism? What does it do?

Answer 17

Beta-galactosidase

• breaks down lactose into glucose and galactose, providing the cell with usable energy

Question 18

How does lactose metabolism help the cell when glucose is absent?

Answer 18

allows the cell to generate glucose internally from lactose

Question 19

How is beta-galactosidase produced? When is the beta-galactosidase gene expressed?

Answer 19

• By turning on transcription of the beta-galactosidase gene
• expressed when lactose is present and glucose is absent

Question 20

what did Francois Jacob & Jacques Monod investigate

Answer 20

how E.coli are able to produce the Beta-galactosidase needed for lactose metabolism

• Observed that the production of the enzyme is dependent on the presence of lactose in the environment

Question 21

how did Francois Jacob & Jacques Monod design their experiment

Answer 21

1. Grew E. coli in a lactose-free medium
2. Added lactose
3. Then removed lactose
4. Measured beta-galactosidase levels throughout

Question 22

Francois Jacob & Jacques Monod: What happened when lactose was added to the medium?

Answer 22

amount of beta-galactosidase steadily increased

Question 23

Francois Jacob & Jacques Monod: What happened when lactose was removed?

Answer 23

production of beta-galactosidase stopped

Question 24

Francois Jacob & Jacques Monod: what did their results demonstrate

Answer 24

• lactose induces (turns on) the expression of the beta-galactosidase gene
• Gene expression in bacteria is regulated by environmental signals, such as the presence of lactose

Question 25

What is gene expression?

Answer 25

refers to a process by which a gene is transcribed (made), translated (converted into protein), and modified & activated

Question 26

What steps must occur for protein-coding genes to be fully expressed?

Answer 26

1. Transcription (DNA → mRNA) 2. Translation (mRNA → polypeptide) 3. Protein modification (activation into functional protein)

Question 27

What are the three levels of gene regulation?

Answer 27

1. Transcriptional control 2. Translational control 3. Post-translational control

Question 28

What does transcriptional control regulate?

Answer 28

regulates the production of mRNA from DNA

Question 29

What does translational control regulate?

Answer 29

regulates the conversion of mRNA into protein

Question 30

What does post-translational control regulate?

Answer 30

regulates the modification and activation of proteins after they are made

Question 31

How does the cell regulate transcription?

Answer 31

By controlling the binding of proteins (e.g., transcription factors) to the promoter region of DNA

Question 32

What happens when proteins bind to the promoter?

Answer 32

They can either: - Activate transcription (increase mRNA production) - Inhibit transcription (decrease mRNA production)

Question 33

Does mRNA always get translated immediately after being made?

Answer 33

No

Question 34

What factor affects how much protein is produced during translation?

Answer 34

The rate of translation

Question 35

How does mRNA stability affect protein production?

Answer 35

- Stable mRNA → more protein produced - Rapidly degraded mRNA → very little protein produced

Question 36

What must happen for a polypeptide to become functional?

Answer 36

It must fold into a 3D structure & undergo post-translational modifications

Question 37

what do post-translation modifications do

Answer 37

They activate or modify proteins through specific chemical changes

Question 38

What happens to a polypeptide as it leaves the ribosome?

Answer 38

It is initially in a linear form, then begins folding into a 3D structure

Question 39

What roles do post-translational modifications play in protein function?

Answer 39

- Promote assembly into protein complexes - Enable binding of substrates - Unmask enzymatic domains (activate enzymes) - Make proteins active or inactive

Question 40

Can all three levels of regulation act on the same gene?

Answer 40

Yes

Question 41

Which level of regulation is the slowest? Why?

Answer 41

Transcriptional regulation - Because the cell must 1) transcribe DNA 2) translate mRNA 3) modify the protein

Question 41

Which level of regulation is the fastest? Why?

Answer 41

Post-translational regulation - Because proteins are already made and stored, and only need quick modification to become active - is an advantage as cells can rapidly respond to signals by activating pre-existing inactive proteins

Question 42

When is transcriptional regulation typically used?

Answer 42

During major environmental changes, such as when glucose is depleted in Escherichia coli

Question 43

Which level of regulation is the most energy-efficient? Why?

Answer 43

Transcriptional regulation - Because the cell does not waste energy making mRNA or proteins unless needed

Question 44

Give an example of efficient transcriptional regulation.

Answer 44

In Escherichia coli: - The beta-galactosidase gene is only expressed when lactose is present - Prevents unnecessary protein production

Question 45

What is the overall advantage of regulating gene expression at multiple levels?

Answer 45

It allows cells to: - Respond quickly (post-translational) - Control protein amounts (translational) - Conserve energy (transcriptional)