How It Works


Gene - a segment of DNA that codes for a specific function like hair color

Base/Nucleotides - the small "puzzle pieces" that make up DNA and RNA, represented by a letter. When you see something like this: AGCTAT this is called a base sequence, because it is a set of ordered bases

Nucleotide pairings
DNA - deoxyribonucleic acid, carries our genetic information, bases: AGCT

RNA - ribonucleic acid, acts as a copy of DNA, bases: AGCU (switch T with U)

CRISPR - a Clustered area of DNA with a Regularly Interspaced Short Palindromic sequence that is Repeated throughout

Cas9 - a protein (a molecule in our body) that cuts DNA at a certain part
DNA strand drawing
  1. A Cas9-RNA complex enters the nucleus of the cell (where the DNA is stored). This RNA is called guide RNA

  2. RNA finds the target area or base sequence on the DNA and binds to it. This triggers the Cas9 protein.

  3. Cas9 unzips the double strands of the DNA, splitting them apart.

  4. If the RNA matches the DNA at that location, the RNA will bind together through their complimentary base pairings (like puzzle pieces)

  5. Cas9 cuts the target DNA sequence, like a pair of scissors. Snip!

  6. Cell senses something odd in its DNA... oh noes! It's been cut! The cell goes to fix it, which may result in:
    1. Disabling a gene (easy)
    2. Fixing the mistake
    3. Inserting a new gene (hard)

  7. Usually, cells try to sloppily glue the two cut strands back together. This usually results in disabling the gene.

    Disabling the gene sounds bad, but it may be what the scientists want! If the gene is a bad gene, such as the malaria-causing gene, then disabling the bad gene is beneficial.

  8. For a visual animation of this process, as well as information on CRISPR's uses, check out this helpful HHMI BioInteractive Website!

    HHMI BioInteractive Link