Question 1

Which of the following best describes a key advantage of using CRISPR-Cas9 over traditional Agrobacterium tumefaciens-mediated plant transformation methods?

Accepted Answer

CRISPR-Cas9 allows for targeted gene editing without the need for foreign DNA integration.

Question 2

In the context of CRISPR-Cas9, what is the function of the PAM sequence?

Accepted Answer

It is required for Cas9 to recognize and bind to the target DNA.

Question 3

A researcher wants to introduce a specific mutation into a plant gene using CRISPR-Cas9. Which repair pathway should be promoted to ensure precise editing, and what is the relevant formula for calculating the probability of successful homology-directed repair (HDR) if the efficiency is $$e$$ and $$n$$ cells are targeted?

Accepted Answer

Homology-directed repair (HDR); Probability = $$1 - (1 - e)^n$$

Question 4

Which of the following best explains why sgRNA (single guide RNA) is used in eukaryotic CRISPR-Cas9 systems instead of separate crRNA and tracrRNA molecules?

Accepted Answer

sgRNA combines the functions of crRNA and tracrRNA, simplifying the system for efficient gene editing in eukaryotes.

Question 5

Which plant hormone is primarily responsible for promoting cell elongation and is involved in phototropism?

Accepted Answer

Auxin

Question 6

A plant exposed to drought stress increases the production of abscisic acid (ABA). What is the primary physiological response mediated by ABA in this scenario?

Accepted Answer

Stomatal closure to reduce water loss

Question 7

Which of the following best describes the role of phytochromes in plants?

Accepted Answer

They act as photoreceptors that regulate responses to red and far-red light, influencing processes such as seed germination and flowering.

Question 8

A short-day plant is transferred from a 16-hour light/8-hour dark cycle to an 8-hour light/16-hour dark cycle. What is the most likely effect on its flowering time?

Accepted Answer

It will flower earlier because the longer night meets its critical night length requirement.

Question 9

Which of the following is a correct sequence of events in the Agrobacterium tumefaciens infection cycle leading to T-DNA integration in the plant genome?

Accepted Answer

Attachment to plant cell, activation of vir genes, T-DNA processing, transfer to plant cell, integration into plant genome

Question 10

Which protein acts as a 'Trojan horse' to facilitate the import of T-DNA into the plant cell nucleus during Agrobacterium-mediated transformation?

Accepted Answer

VIP1

Question 11

A plant is genetically engineered to express a hairpin RNA targeting a viral gene. Which RNA silencing pathway is primarily activated, and what is the expected outcome?

Accepted Answer

siRNA pathway; degradation of viral RNA

Question 12

Which of the following best describes the role of jasmonic acid in plant defense?

Accepted Answer

It mediates defense responses against herbivorous insects and necrotrophic pathogens.

Question 13

A mutation in a plant's MAPK cascade results in the inability to activate defense genes after pathogen detection. Which step in the signal transduction pathway is most directly affected?

Accepted Answer

Phosphorylation of downstream transcription factors

Question 14

Which of the following terms refers to the plant's ability to develop long-lasting, broad-spectrum resistance after an initial pathogen attack?

Accepted Answer

Systemic acquired resistance (SAR)

Question 15

Which of the following best explains how plants can use RNA interference (RNAi) to defend against viruses, and how some viruses counteract this defense?

Accepted Answer

Plants produce siRNAs that degrade viral RNA, while viruses may encode suppressor proteins that inhibit the RNAi machinery.

Question 16

Which of the following is a direct result of ubiquitination in plant signal transduction pathways?

Accepted Answer

Targeted protein degradation via the proteasome

Question 17

A plant scientist wants to induce multiple gene knockouts simultaneously using CRISPR-Cas9. Which strategy should be used?

Accepted Answer

Multiplexing with multiple sgRNAs targeting different genes

Question 18

Which of the following best describes the function of a receptor-like kinase (RLK) in plant immunity?

Accepted Answer

It perceives pathogen-associated molecular patterns (PAMPs) and initiates downstream signaling.

Question 19

Which process is most directly linked to epigenetic regulation in plants and can be influenced by RNAi mechanisms?

Accepted Answer

DNA methylation

Molecular Plant Sciences: Genetic Engineering, Signaling, and Stress Responses

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