Week 9 - Molecular Regulation

Question 1

What is the primary function of the LacI gene in the lac operon system?

A) To promote lactose metabolism
B) To encode a protein that represses the lac operon
C) To facilitate the binding of RNA polymerase
D) To produce an allosteric protein that activates the operon

Answer 1

Answer: B) To encode a protein that represses the lac operon

Question 2

Which of the following statements is true about the lac operon?

A) It is a positively controlled system.
B) It is always expressed regardless of lactose presence.
C) It is a polycistronic gene encoding multiple proteins.
D) It requires glucose to be activated

Answer 2

Answer: C) It is a polycistronic gene encoding multiple proteins.

Question 3

In the trp operon, which condition leads to the activation of the trp repressor?

A) High levels of tryptophan
B) Low levels of tryptophan
C) Presence of glucose
D) Absence of lactose

Answer 3

Answer: A) High levels of tryptophan (opposite process of the lac operon)

Question 4

What role does cAMP play in the regulation of the lac operon?

A) It directly inhibits the lac repressor.
B) It activates the lac operon by binding to the CAP.
C) It enhances the transcription of the trp operon.
D) It degrades lactose in the cell

Answer 4

Answer: B) It activates the lac operon by binding to the CAP

Question 5

Which of the following accurately describes catabolite repression?

A) It promotes the use of lactose over glucose.
B) It prevents the synthesis of enzymes when glucose is present.
C) It activates all operons in the presence of glucose.
D) It is a mechanism found only in eukaryotic cells

Answer 5

Answer: B) It prevents the synthesis of enzymes when glucose is present

Question 6

What is the effect of adding glucose to E. coli when lactose is also present?

A) Increased transcription of the lac operon
B) Decreased transcription of the lac operon
C) Activation of the trp operon
D) No effect on transcription

Answer 6

Answer: B) Decreased transcription of the lac operon

Question 7

What is the significance of the operator in operon regulation?
A) It is where RNA polymerase binds to initiate transcription.
B) It is the site where transcription factors enhance gene expression.
C) It is where repressor proteins bind to inhibit transcription.
D) It determines the direction of transcription.

Answer 7

Answer: C) It is where repressor proteins bind to inhibit transcription.

Question 8

In spatial signaling during development, which gene is crucial for establishing axial polarity in plants?

A) LacI gene
B) CAP gene
C) Gnom gene
D) Bicoid gene

Answer 8

C) Gnom gene

Question 9

What role does bicoid mRNA play in early embryonic development?

A) It encodes enzymes for tryptophan biosynthesis.
B) It establishes a protein gradient determining the anterior-posterior axis.
C) It activates the lac operon in the zygote.
D) It signals for apoptosis in developing tissues.

Answer 9

Answer: B) It establishes a protein gradient determining the anterior-posterior axis.

Question 10

How does the GLABRA-2 gene influence root hair development in Arabidopsis thaliana?

A) It promotes the formation of root hairs in all cells.
B) It acts as a repressor in cells that do not develop root hairs.
C) It signals for the apoptosis of root hair cells.
D) It is responsible for lateral root formation.

Answer 10

Answer: B) It acts as a repressor in cells that do not develop root hairs

Question 11

Which enzyme is essential for joining DNA fragments together after cutting?

A) DNA polymerase
B) Ligase
C) Restriction endonuclease
D) Helicase

Answer 11

Answer: B) Ligase

Question 12

What type of DNA sequences do restriction endonucleases typically recognize?

A) Linear sequences
B) Palindromic sequences
C) Circular sequences
D) Random sequences

Answer 12

Answer: B) Palindromic sequences

Question 13

In the Polymerase Chain Reaction (PCR), what is the role of primers?

A) To unwind the DNA strands
B) To provide a starting point for DNA synthesis
C) To degrade non-target DNA
D) To inhibit the replication of unwanted sequences

Answer 13

Answer: B) To provide a starting point for DNA synthesis

Question 14

What is a characteristic feature of Taq polymerase that makes it suitable for PCR?

A) It works best at room temperature.
B) It can withstand high temperatures without denaturing.
C) It is highly specific to eukaryotic DNA.
D) It requires a helicase for function.

Answer 14

Answer: B) It can withstand high temperatures without denaturing

Question 15

Which of the following is a result of the accumulation of signals during cellular differentiation?

A) Apoptosis
B) Gene expression regulation
C) Increased cellular apoptosis
D) Enhanced metabolic activity

Answer 15

Answer: B) Gene expression regulation

Question 16

How does the presence of tryptophan affect the trp operon?

A) It activates transcription of the operon.
B) It inhibits the binding of RNA polymerase.
C) It leads to the activation of the trp repressor.
D) It promotes the synthesis of lac operon enzymes

Answer 16

Answer: C) It leads to the activation of the trp repressor / turns off the trp operon

Question 17

Which component is responsible for the negative control in both the lac and trp operons?

A) CAP protein
B) RNA polymerase
C) Repressor proteins
D) Operon structure

Answer 17

Answer: C) Repressor proteins

Question 18

What is the primary method of gene amplification in a laboratory setting?

A) Cloning
B) Gene editing
C) Polymerase Chain Reaction (PCR)
D) Gel electrophoresis

Answer 18

Answer: C) Polymerase Chain Reaction (PCR)

Question 19

How is the transcription factor CAP activated?

A) By binding to high levels of glucose
B) By binding to cAMP when glucose levels are low
C) Through direct interaction with RNA polymerase
D) By the presence of tryptophan

Answer 19

B) By binding to cAMP when glucose levels are low

Question 20

What kind of system is the lac operon system?

Answer 20

a negatively controlled AND inducible system

Question 21

What kind of system is the trp operon?

Answer 21

a negatively controlled AND repressible system

Question 22

What kind of system is the lac operon + glucose?

Answer 22

a positively controlled and inducible system

Question 23

What part of the promoter does the negative control?

Answer 23

the operator

Question 24

Which staining method distinguishes DNA from proteins by coloring DNA blue and proteins pink?
A) Silver staining
B) Ethidium bromide staining
C) Hematoxylin staining
D) Fluorescence in situ hybridization

Answer 24

Answer: C) Hematoxylin staining

Question 25

What type of DNA ligase is typically used at room temperature and can work with both sticky and blunt ends?

A) DNA Ligase I
B) T4 DNA ligase
C) Taq ligase
D) Restriction ligase

Answer 25

Answer: B) T4 DNA ligase

Question 26

What is a palindromic sequence in the context of DNA?

A) A sequence that can be read the same forward and backward
B) A sequence that can replicate itself
C) A sequence that is exclusively found in eukaryotic DNA
D) A sequence that binds to restriction enzymes

Answer 26

A) A sequence that can be read the same forward and backward

Question 27

What is the purpose of using ethidium bromide in gel electrophoresis?

A) To cut DNA into fragments
B) To stain and visualize DNA
C) To amplify DNA
D) To join DNA fragments

Answer 27

Answer: B) To stain and visualize DNA

Question 28

During PCR, what is the purpose of the annealing step?

A) To separate DNA strands
B) To synthesize new DNA strands
C) To allow primers to bind to target sequences
D) To denature the DNA polymerase

Answer 28

Answer: C) To allow primers to bind to target sequences

Question 29

Which enzyme is used for the synthesis of new DNA strands during PCR?

A) DNA helicase
B) DNA ligase
C) DNA polymerase
D) RNA polymerase

Answer 29

Answer: C) DNA polymerase

Question 30

What is the typical melting temperature for DNA strands during the PCR process?

A) 50-60°C
B) 70-80°C
C) 90-95°C
D) 30-40°C

Answer 30

Answer: C) 90-95°C

Question 31

What is the expected result after 30 cycles of PCR starting with a single DNA molecule?

A) 30 copies
B) 60 copies
C) 1 billion copies
D) 2 billion copies

Answer 31

Answer: C) 1 billion copies

Question 32

What type of application would involve the use of recombinant DNA?

A) Visualizing protein structures
B) Creating genetically modified organisms
C) Amplifying DNA sequences
D) Staining DNA for microscopy

Answer 32

Answer: B) Creating genetically modified organisms

Question 33

What defines an enzyme as a restriction endonuclease?

A) It ligates DNA fragments together.
B) It cuts DNA at random locations.
C) It recognizes specific DNA sequences and cleaves them.
D) It synthesizes DNA from RNA templates

Answer 33

Answer: C) It recognizes specific DNA sequences and cleaves them

Question 34

In what scenario would you use site-directed mutagenesis?

A) To amplify a gene
B) To create a recombinant organism
C) To introduce specific mutations into a DNA sequence
D) To cut DNA into smaller fragments

Answer 34

Answer: C) To introduce specific mutations into a DNA sequence

Question 35

How does Taq PCR work at a molecular level? (5)

Answer 35

1. Melting = complementary strands melt apart
2. Annealation = find their complementary sequences where it complements the 5’ to 3’ end
3. After extension with Taq = extension step extends one strand of DNA to its new 3’ prime end and same with the other one
4. Repeat: after melting again: the original and copy strands act as templates, so more primers annealing and extending to make more strands in truncated strands,
   The copies will be the final product with primer binding sequence on both ends, 2^30 copies - minus 30 copies from original long copies