Book Club: The Double Helix

doublehelixIn case you missed why I’m creating a book club, check out my previous post.

The first book in the book club is The Double Helix written by the Nobel Prize winner James Watson.  He won the Nobel Prize along with Francis Crick and Maurice Wilkins in 1962 by discovering the structure of DNA (learn more about DNA in my earlier post What is DNA?).  This is a provocative book written by a provocative scientist about how he came to discover this structure (a great review of the book can be found here).  Much of it deals with the relationship with Rosalind Franklin, the scientist who created the images that provided Watson with the information that allowed him to determine the structure, and his other colleagues. This book also gives you insight into the mind of a scientist (though please don’t use this book to judge all scientists because his personality really is a unique one). If you’re interested in the original scientific publication, you can find it here – it’s incredibly short, considering its significance.

After my mom read this book, she put it down and asked me “I understand that they solved the structure and all, but why was it so important?” This was so important because this structure indicated that the bases (described here) paired together: A with T and G with C.  This meant that the sequence of either strand could be used as templates to copy the DNA. Copying DNA needs to be done every time a cell divides – and considering that humans (who have 37 trillion cells) come from one original cell (the fertilized egg), that’s a LOT of dividing that needs to be done.

An interesting aside – I’ve met and talking with Jim Watson many times since he was the Chancellor at the graduate school I attended.  He was an interesting character.  His legacy is very much defined by this discovery, but also of his vision for the laboratory that he ran on Long Island, Cold Spring Harbor Laboratory.  My Mom has met him several times as well, and I suppose both of us can legitimately say that we have learned a few things from a Noble Prize winner.

For more Book Club books, click here.

What is DNA?

There’s so much to know about science and biology that requires background information.  This may be tedious to read, but it’s essential to understanding so much of how things work (or don’t, in the case of disease).  Many of my posts will provide this kind of background, and they will also be archived in the “Background Info” menu for future reference.  If this is old hat to you, that’s okay!  If not, please read and learn – it’s worth taking the time so that future posts make more sense.

So probably everyone knows what DNA is. Right?  It’s talked about on the news all of the time.  Maybe vaguely it’s defined in your head as “the building block of life”.  Maybe you know about the double helix (more on that soon!!).  Maybe you’ve even isolated DNA as part of a science fair experiment.  But really, WHAT IS IT?

dna double helixI remember the first time I learned what DNA was in a biology class.  The biology book’s fourth chapter was entitled “Marcomolecules” and one of these molecules was DNA.  It was confusing.  All the different macromolecules were introduced all at one time.  I had no idea how they were related to one another or why I was learning about them.  And why were they called macro?  That implied big, and I knew for a fact that DNA was small (because it has to fit in a cell!) So let’s break down what DNA really is, in a way that I hope is far less confusing than my first biology book.

DNA is the genetic code that makes up all of human life – or any life on earth (yes, your DNA is made up of the same parts as angler fish DNA or tulip DNA) .  A lot of times, people compare it to a blueprint, where the DNA provides the instructions to make whatever organism it is supposed to create.  This is essentially true.  DNA itself is made up of individual parts called nucleotides.  There are four nucleotides – each containing a different base:GCAT

  • Adenine (A)
  • Thymine (T)
  • Guanine (G)
  • Cytosine (C)

These are often abbreviated using the single letter listed above – A, T, G or C.  These bases are each associated with a sugar and a phosphate, which forms what is commonly referred to as the “backbone” of DNA.  Look at the picture above to see what this looks like.  DNA looks like a ladder – the sugar and phosphate forms the sides of the ladder (the light blue in the picture) and the bases form the rungs.  What’s really neat and interesting is that these bases don’t pair up randomly.  Adenine always pairs up the Thymine and Guanine always pairs up the Cytosine. Want to know why?  Well, it’s because of the shape of the bases.  Take a look at the pictures above. A and T have two places where they can bind to each other and G and C have three.  If you tried to get an A to bind to a C, it wouldn’t work because the C would have an empty binding spot hanging out there.

replicationSo why in the world is this important at all?  Well, think of this – because we know this rule, if we know the sequence of As, Ts, Gs and Cs of one strand of the DNA ladder, we also know sequence of the other strand.  This means that when DNA copies itself (what scientists call replication), two copies of the DNA can be made relatively easily: the ladder unzips and each separate side of the ladder functions as a template to make two exact copies of the DNA.  This process happens 10,000 trillion times in your lifetime.

There are so many interesting things about DNA and how it works – all will be discussed in future posts.  But in case you want more information right now, I have compiled interesting DNA references can be found here.