CRISPR #1 - Basics of Biology

In his book, The Code Breaker, on gene editing technologies, Walter Isaacson makes an interesting observation. In the 1950’s, information theory was developed – how information can be encoded. (The most well-known example of this today are the 1’s and 0’s, the bits and bytes of computer science). But around that same time, Watson and Crick discovered the famous double helix structure of DNA. Unlike computer bits, DNA is coded in a 4-letter alphabet of A, T, G and C. But the similarity is clear – it’s all about information. And:

“The flow of history is accelerated when two rivers merge.”

As the code of DNA began to be understood (to some extent, at least), it became clear that DNA was like an instruction manual – it had all the information. But it didn’t do anything.

“DNA doesn’t do much work. It mainly stays at home in the nucleus of our cells, not venturing forth.”

Biologists began to understand the role of RNA:

“RNA… actually goes out and does real work. Instead of just sitting at home curating information, it makes real products, such as proteins.”

 

Many of us think of proteins as being the stuff that repairs the body and/or leads to growth. But proteins do many other things. Fibrous proteins form structures e.g. bones, hair, muscles, tissues. Membrane proteins relay signals within cells. And then there are the proteins called enzymes – they are catalysts that enable, accelerate and modulate the chemical reactions within our body.

 

This then is what Watson called the “central dogma” of biology – genetic information moves from DNA to RNA to build proteins. Watson admitted the word “dogma” was a bad choice of words since it means “unchanging and unquestioned faith”. But the word “central” is certainly apt.

 

Of course, nothing in biology is ever so simple or clear cut. Biology is full of exceptions, deviations, hacks and, er, whatever works. In that sense, biology is like engineering! Scientists would discover that some forms of RNA could be enzymes (instead of building proteins) – these were called ribozymes. It turned out that there are parts of DNA called introns that don’t code for proteins – they just clog things up as far as the RNA is concerned. So the RNA cuts and removes such chunks of DNA from itself – the term for this is splicing.

 

For a long time, biologists believed that DNA was key (it was the instructions, after all) and proteins were what did most of the work. The RNA, in this view, was a “dull intermediary, sort of a middle manager”. That view would change with the advent of CRISPR…