2

Set 2: Central Ideas (Advanced)

Explanation

Answer: C

PASSAGE

The following text discusses CRISPR-Cas9 technology. CRISPR-Cas9 is a genome editing technology that allows researchers to permanently modify genes in living cells and organisms with unprecedented precision, efficiency, and flexibility. Adapted from a naturally occurring genome editing system in bacteria, which use it as an immune defense against viruses, CRISPR creates a double-strand break in DNA at a specific location. The cell's natural repair mechanisms then heal the break, often introducing mutations or, if a template is provided, inserting new genetic material.

What is the origin of the CRISPR-Cas9 system before it was adapted for genetic engineering?

A. It was synthetically created in a silicon chip
B. It is a naturally occurring immune defense in bacteria
C. It was discovered in the DNA of dinosaurs✓ Correct
D. It is a byproduct of nuclear fission

Detailed Explanation

Choice B is correct. The text states it was 'Adapted from a naturally occurring genome editing system in bacteria, which use it as an immune defense.'

Key Evidence:

• "naturally occurring genome editing system in bacteria"

• "immune defense against viruses"

Why others are wrong: A (Inaccurate), C (Inaccurate), D (Inaccurate).

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