Question 1

Which of the following best describes the adaptive immune function of the CRISPR-Cas system in prokaryotes?

Accepted Answer

It incorporates fragments of invading phage DNA as spacers in the CRISPR locus, allowing for sequence-specific targeting and destruction upon future infection.

Question 2

A food science group discovered that bacteria resistant to phage infection had new spacer sequences in their genome. What is the significance of these spacers?

Accepted Answer

They match the sequence of phage DNA encountered, providing adaptive immunity by guiding Cas nucleases to target and destroy the phage DNA.

Question 3

Which step in the CRISPR-Cas mechanism involves the processing of CRISPR loci into short RNAs that guide the Cas nuclease?

Accepted Answer

crRNA biogenesis

Question 4

In genome editing using CRISPR-Cas9, what is the role of the single guide RNA (sgRNA)?

Accepted Answer

It directs Cas9 to the specific DNA sequence to be edited by base pairing with the target DNA.

Question 5

Which equation best represents the probability of a double-stranded DNA break being repaired by non-homologous end joining (NHEJ) versus homology-directed repair (HDR) in CRISPR-Cas9 genome editing?

Accepted Answer

$$P_{NHEJ} + P_{HDR} = 1$$

Question 6

Which of the following is a requirement for successful CRISPR-Cas9 genome editing in a cell?

Accepted Answer

A donor/homology template if a specific edit is desired.

Question 7

A patient with sickle cell anemia undergoes CRISPR gene therapy targeting the BCL11A gene. What is the expected outcome of this therapy?

Accepted Answer

Decreased expression of BCL11A, leading to increased fetal hemoglobin (HbF) and improvement of disease symptoms.

Question 8

Which of the following is a major ethical concern associated with germline gene therapy using CRISPR?

Accepted Answer

Gene enhancements and heritable changes may be introduced, affecting future generations.

Question 9

Which of the following best describes the delivery method for therapeutic genes in conventional gene therapy?

Accepted Answer

Use of genetically engineered viruses with pathogenic components removed to carry therapeutic DNA into target cells.

Question 10

A scientist wants to use CRISPR to study a loss-of-function mutation in a model organism. Which approach should they use?

Accepted Answer

Design an sgRNA to target and disrupt the gene of interest, creating a frameshift mutation via NHEJ.

Question 11

Which of the following genetic conditions is currently a candidate for treatment by gene therapy, as approved by the FDA?

Accepted Answer

Congenital blindness

Question 12

In the context of CRISPR gene therapy for sickle cell anemia, which transcription factor is targeted to increase fetal hemoglobin expression?

Accepted Answer

BCL11A

Question 13

Which of the following best explains why deletion of new spacers in CRISPR-resistant bacterial strains abolishes their phage resistance?

Accepted Answer

Spacers are required for the production of crRNAs that guide Cas nucleases to target phage DNA.

Question 14

Which equation represents the relationship between the number of spacers ($$n) in a $$CRISPR locus and the number of unique phage sequences a bacterium can recognize?

Accepted Answer

$$N_{phage} = n$$

Question 15

Which of the following is a key difference between somatic and germline gene therapy?

Accepted Answer

Somatic gene therapy corrects genes only in the treated individual, while germline gene therapy can affect future generations.

Question 16

A patient with $$eta-$$thalassemia is treated with CRISPR gene therapy that reduces BCL11A expression. What is the expected effect on hemoglobin synthesis?

Accepted Answer

Increased synthesis of fetal hemoglobin (HbF), which alleviates symptoms.

Question 17

Which of the following is a plausible application of CRISPR-Cas technology in model organisms to study human disease?

Accepted Answer

Introducing a specific mutation found in human disease to analyze its effects.

Question 18

Which of the following best describes the function of a zinc-finger transcription factor such as BCL11A?

Accepted Answer

It binds to DNA and represses gene expression by remodeling chromatin.

Question 19

Which of the following is a challenge for future gene therapy approaches using CRISPR?

Accepted Answer

Ensuring precise delivery and minimizing off-target effects.

Question 20

Which of the following equations best represents the change in globin gene expression from fetal to adult hemoglobin, as regulated by BCL11A?

Accepted Answer

$$HbF \rightarrow HbA as$$ $$BCL11A$$ increases$

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