gen-define-crispr-gene-editing-and-give-one-short-worked-example-aed2

Define CRISPR gene editing and give one short worked example.

# CRISPR Gene Editing **CRISPR** (Clustered Regularly Interspaced Short Palindromic Repeats) is a precise molecular tool that allows scientists to edit DNA sequences in living organisms. It works like "molecular scissors" - the Cas9 protein cuts DNA at a specific location guided by a piece of RNA, allowing genes to be removed, added, or altered. ## How it works: 1. **Guide RNA** is programmed to match a target DNA sequence 2. **Cas9 protein** binds to the guide RNA and scans DNA for the matching sequence 3. When found, Cas9 **cuts both strands** of DNA 4. The cell's repair mechanisms fix the break, allowing scientists to: - Disable a gene (by introducing errors) - Insert new genetic material - Correct mutations ## Worked Example: Treating Sickle Cell Disease **Problem:** Sickle cell disease is caused by a single mutation in the hemoglobin gene (HBB), producing abnormal, sickle-shaped red blood cells. **CRISPR Solution:** 1. Extract patient's bone marrow stem cells 2. Use CRISPR to edit the BCL11A gene, which normally suppresses fetal hemoglobin production 3. Disabling BCL11A reactivates fetal hemoglobin (which doesn't sickle) 4. Return edited cells to patient **Result:** The patient produces healthy fetal hemoglobin instead of defective adult hemoglobin, eliminating sickle cell symptoms. This approach has shown remarkable success in clinical trials, with patients achieving complete remission.