The CRISPR-Cas9 system, borrowed from prokaryotes, is like the "find and replace" function in a word processor, but for genes! Let's break it down.

C.R.I.S.P.R: Like the crisps you munch on? Not really! It stands for Clustered Regularly Interspaced Short Palindromic Repeats. Here's what each word means

• Repeats: Same base sequence pops up multiple times.
• Short: Just between 23 and 47 base pairs. Tiny, right?
• Clustered: All grouped together like a reunion.
• Regularly Interspersed: Between these repeats are unique sequences called spacers. Think of them as dividers in a cookie box.
• Fun fact: these spacers come from viruses that tried to attack the prokaryotes. It's like a genetic "Most Wanted" poster!
• Palindromic: Reads similarly backward and forward (almost).

• It's a natural enzyme, acting like a DNA detective.
• Its partner-in-crime is guide RNA (gRNA) that's derived from a CRISPR array.
• As it moves along DNA, it seeks out specific sequences to match with its gRNA.
• Once it finds a match, it performs a snip-snip action, cutting through the DNA.

💡 Real-world example: Imagine a barcode scanner scanning products to find a match. Cas9 is the scanner, and the gRNA is the barcode it's looking for.

• Scientists always wanted a tool like search and replace for genes. Enter CRISPR-Cas9!
• Prime editing: An improved method using special RNA, pegRNA. It's kind of like CRISPR 2.0.
  • This RNA connects with modified Cas9, looking for target genes.
  • When found, instead of a double-cut, it makes a single cut (nick) in the DNA.
  • Using a feature of pegRNA, new genetic information is added, replacing the old.
  • Our body's natural repair system takes over from here, fixing any mismatches.

💡 Real-world example: It's like using an advanced software patch to fix bugs in a program. The software (CRISPR) searches for the bug (specific gene sequence), then patches it (modifies it)!