CRISPR: editing a chosen DNA sequence — Biology, 14–17
CRISPR uses a guide sequence to bring a cutting protein to a chosen place in DNA. The cell’s repair system then changes that site, making precise experiments possible but never perfectly predictable.
A guide brings a molecular tool to one place
In CRISPR, a short guide sequence is designed to match a chosen DNA region. It pairs with that region and positions an associated protein there. The protein cuts the DNA, and the cell repairs the break. Researchers can use that repair to disrupt, replace or alter a sequence.
Why targeted editing was needed
Older genetic methods could add DNA or cause random changes, but researchers often needed to test one gene without disturbing many others. CRISPR addresses that problem by aiming at a chosen sequence. It came from a bacterial defence system, where guide RNA helps recognise invading genetic material.
Disabling one gene in cells
Suppose a gene makes a fluorescent protein. First, researchers choose a guide matching that gene. Second, CRISPR cuts inside its coding sequence. Third, repair may insert or delete a few DNA bases. If the number is not a multiple of three, the reading frame shifts, often producing a broken protein. The result must then be tested.
“Targeted means perfectly controlled”
The name CRISPR can make editing sound like changing one letter with no side effects. In reality, the guide may bind to a similar DNA sequence elsewhere, and the cell’s repair can produce different outcomes. Scientists therefore sequence the DNA and compare treated cells with proper controls.
Research, crops and possible therapies
Researchers use CRISPR to switch genes off and discover what they do, or to give cells a corrected version to study. It is also being investigated for crops and treatments for some inherited diseases. Changing cells in a dish is not the same as safely changing a whole person, so evidence and ethics matter.
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