Molecular Scissors: Restriction Enzymes

Molecular Scissors: Restriction Enzymes

Microbial Underworld: Imagine a cut throat, competitive underworld where intruders are efficiently decimated by a custom-made weapon that slashes right through their life lines. These ancient molecular scissors evolved in bacteria to defend against parasitic viruses, called ‘phages. Better known as restriction endonucleases, these enzymes recognize a specific DNA sequence as their target. A short 6-8 letter sequence effectively marks the hapless victim for destruction. How does the host go unscathed? The same sequence is protected by a chemical modification (methylation) that makes it invisible to a veritable incarnation of Edward Scissorhands.

Snip, Snip! The molecular scissors are named after the bacteria of origin. For example, Eco RI signifies that it was from the E. coli bacterium. Several thousand have been discovered, that recognize some 200 unique sequences. A favorite of the biologist’s tool kit recognizes palindromic sequences, that read the same forward or backward.

Here’s one, that snips straight through (cuts indicated by |), making blunt ends:

                             CCC|GGG

                             GGG|CCC

Here’s another that makes a staggered cut, better known as sticky ends:

                            GA|ATTC

                            CTTA|AG

Nobel Find: The scientists who discovered restriction endonucleases (two from my home ground, Dan Nathans and Ham Smith, along with Werner Arbor) were honored with the Nobel prize. These molecular scissors gave birth to new fields of Recombinant DNA technology and more recently, Synthetic Biology.  We can now cut and paste genes, clone and copy them, and move them in or out of cells, thanks to these precise cutting tools (together with handy glue in the form of ligases or joining enzymes).

Image: Eco RI wrapped around model DNA, by John M. Rosenberg via http://goo.gl/OGb5N

This post is to celebrate the birthday of Kawthar AL ABDALLA , who is beautiful both inside and out. Watch out, Kawthar uses ✄ as effectively as a restriction enzyme!

#KKScissorHands #whatever #HappyBirthdayKawthar #ScienceEveryday  

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29 Responses to Molecular Scissors: Restriction Enzymes

  1. Jim Carver says:


    Slicing through into the future…but will the future be as glad as you hoped?

  2. Rajini Rao says:


    That’s not ours to reason why from Tennyson’s Charge of the Light Brigade. I just made a comment on Gerd’s synthetic biology post: Science is neither evil nor good, how it is used is often determined by people outside science. This includes politicians, businessmen and entrepreneurs.

  3. Rajini Rao says:


    It’s an exciting time, Chadwick Jones . But funds are tight.

  4. Ron Scroggin says:


    I remember how to cut and splice audio tape — I can do this…

  5. Tina Hardin says:


    wow this is so cool. if we can simply “snip” small invasive cells, imagine what we could do to refine nanotechnology that a small lazer could ruin!

  6. Rajini Rao says:


    Same splice and dice action, different information Ron Scroggin 🙂

  7. Gary Ray R says:


    Well written, easy to understand explanation, that even an old engineer can understand.  Thanks.  


    I like those little scissors for bullet points. Clever.

  8. Rajini Rao says:


    Tina Hardin , cells are huge compared to these little tools. They can snip at molecules a lot smaller (and inside) cells…effectively killing them from within. The trick is to figure out how to target them to only the nasty, invasive type we want to remove.

  9. Rajini Rao says:


    Oh yes, there is an excellent video narrated by Drew Endy that explains it very well. These “transcriptor” switches are a clever use of natural biological switches that turn the copying machinery of genes on/off. They’ve been arranged to work like logic gates. Excellent new tool for synthetic biologists!

  10. Rajini Rao says:


    Bio-programming goes much further than a trim, Peter Lindelauf . Some men are familiar with it already, it’s called male pattern baldness 🙂


  11. Thanks for good educative information.

  12. Kawthar A says:


    Oh…so sweet of you Rajini, thanks ❤


    And as you said, watch out people 😉 have a nice day dear! 🙂

  13. Deeksha Tare says:


    Thanks for the share Rajini Rao 🙂


    Restriction enzymes was my favorite topic in college!

  14. John Kellden says:


    The future of learning, today, delivered by Rajini Rao – big thanks for your long series of excellent posts.

  15. Alice Haugen says:


    Reminds me of a fun session, many years ago, at my daughter’s elementary school when I did a demonstration of restriction enzymes as “magic scissors” that could find the right place to cut and cut only there.

  16. Rajini Rao says:


    Alice Haugen , what a clever idea!

  17. Hamad AZ says:


    Rajini Rao very interesting! Its really not much what you can find about mol. Biol. On G+


    Kawthar AL ABDALLA may I ask about your field?

  18. Rajini Rao says:


    Hamad AZ , thanks. Have you checked out Science on Google+: A Public Database ? You can add your profile to the database and follow other scientists from specific disciplines. 

  19. Rajini Rao says:


    Haha, I’ll keep that in mind. I hope the scissors get a pass this time 🙂


  20. 94,301 have her in circles. Yikes! I thought Tom had a lot.

  21. Hamad AZ says:


    Rajini Rao thanks!

  22. Rajini Rao says:


    Glad you found this useful, Rebecca K 🙂


  23. how come you find time to post everything so useful everyday.. I am in grad school and trust me ..all the time I spend is in lab 😦

  24. Susan LaDuke says:


    Rajini Rao Thanks again! Appreciate the informative shares you post!

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