"DNA neither cares nor knows. DNA just is. And we dance to its music." - Richard Dawkins

Deoxyribonucleic acid.  My first memory of that phrase was from watching Bill Nye the Science Guy in elementary school (Hey, I’m pretty sure you all watched that show, so don’t call me a nerd!).  I could barely pronounce the whole thing.  I remember my friends and I would have contests to see who could say it the most number of times in a minute without faltering.  Little did I appreciate this building block of life until I attended a summer science camp before my senior year of high school (OK, I’m a nerd). 

The 3-week intensive program consisted of classes in various areas of math and science as well as lab sessions. In our biology lab session, we extracted DNA from vegetables (you can do it yourself!).  It was pretty cool to have the genetic material of an onion right at my fingertips (well, pipette tip).  It doesn’t look anything special, though.  It’s white and stringy, and no, you can’t see the actual double helix! We also performed PCR (polymerase chain reaction), a process that amplifies DNA in order to create a sufficient amount of it to properly analyze the product. 

 

I soon found out later in my research career that PCR pretty much defines the life of a scientist.  We use it so much that songs have been made about PCR and its reagents.  The PCR products are eventually run on a gel.  If this sounds foreign to you, think CSI.  This is how they figure out who the murder is (and even who the daddy is! Refer to the first PCR song).  Basically, DNA is injected into an agar block with wells indented into it.  I was initially terrified of injecting the DNA because if you pushed the tip too far into the gel, the DNA would leak out of its designated well, all hell would break loose, toilets would start flushing in the opposite direction, and your dreams of becoming a scientist were shattered (or so I thought).  Believe me, one needs steady arms and hands for loading the DNA, but now I can practically do it in my sleep!  The tray containing the gel with the DNA loaded on it is put in a box hooked up to a voltage source.  When the current is turned on, the DNA migrates down the gel, moving from the negative to positive electrode. Why? DNA is a negative molecule, so naturally, it is attracted to the positive charge! After running the gel for about 30 minutes, it is viewed under UV light.  The gel is previously stained with ethidium bromide, which physically interacts with the DNA, allowing the DNA to fluoresce under UV light.  A ladder with known DNA sizes is also run along the DNA.  Thus, one can estimate the size of the DNA based on the ladder size.  And voila!  Now you know “who dunnit” based on whether the sizes of the victim's and suspect's DNA match up.  Of course, this technology is not only used to solve crimes, but also to help make many scientific discoveries!

 

This lab experience made me realize not only how important DNA is to life but even to applications in life.  Now I am passing on this skill to middle school students!  Through a science outreach program, I helped some grad student TAs with a lab in which the kids themselves extracted DNA from their cheeks and practiced loading gels (they were much better than I was on my first try!).

 

I came to appreciate the history of DNA when I studied abroad in King’s College London during the fall semester of my Junior year.  It was here that Rosalind Franklin and Maurice Wilkins used X-ray diffraction to understand the physical structure of the DNA molecule, during the fall semester of my Junior year.  I saw the semi-original model made famous by James Watson and Francis Crick, displayed in the Science Museum in London.

Semi-original DNA model. London Science Museum.

Seeing the model made me realize how the simple beauty of the nucleotide base pairing that occurs to create this double helix. Why did nature decide to just stick to two strands?  Linus Pauling, who won the Nobel Prize in Chemistry in 1954 for his work on chemical bonds and crystal structures, published a paper in 1953 where he proposed that DNA existed as a triple helix.  Watson and Crick also incorrectly calculated the DNA to be a triple helix in 1951 based on Watson incorrectly remembering the facts and figures from a talk by Rosalind Franklin, who was working on the DNA X-ray crystallography data at King’s College. It was actually Franklin's "photograph 51", a picture of crystallized DNA that showed an “X” in the middle of the molecule, thus revealing the helical structure.

A few weeks later I visited Cambridge. I saw the outside of the Cavendish lab where Watson and Crick worked out the structure of DNA, and had lunch at the Eagle, the pub where Watson and Crick frequently discussed their ideas. Most of what I knew about Watson was of his early years at this lab.  I had not kept up with his recent musings until I had planned to attend a lecture by Watson at the museum. Unfortunately, a week before the lecture, he made his infamous remark questioning the intelligence capacity of people of African descent. 

 

Yeah, DNA is pretty awesome (all you protein lovers ain’t got nothin’ on us!).  As a grad student I am studying DNA modifications in immune cells. My work in undergrad focused mainly on nucleic acid research, but specifically on RNA, DNA’s alter ego. This post is dedicated solely to DNA, but to find out more about the RNA world hypothesis, which states that RNA was existed way before DNA and proteins, check out this page from the Nobel prize site: http://nobelprize.org/nobel_prizes/chemistry/articles/altman/, or check out the book The RNA World, 3^rd Ed.