DNA. We all know it as the building block of life, the very substance that makes us so similar and yet so different.
The discovery of DNA's double-helix structure revolutionized the field of science and medicine. It helped scientists better understand how DNA replicates as cells in our bodies grow. But it also raised more questions - what would happen if the replication mechanism were to go wrong?
Last week, three scientists -- Tomas Lindahl, Paul Modrich and Aziz Sancar, were awarded the Nobel Prize in Chemistry for discovering the mechanism by which cells repair DNA.
Our Body's Blueprint
Every nucleus in every cell in our body has DNA. Large stretches of DNA are called "chromosomes" and portions of chromosomes are called genes. DNA provides the instructions that cells need in order to carry out their basic jobs.
Think of a library. A chromosome is like a thick book,and genes are like chapters in the book. The letters in the book are all DNA code. DNA is made up of four chemicals which go by the initials A, T, G, C. So the chapters will read something like this: AATTCGCATACGGAA and so on - nonstop, no breaks!
When Watson and Crick uncovered the DNA's double-helix (twisted ladder) structure, they found that the two DNA strands are connected to each other only at some points -- where chemicals A and T bond with each other, as do C-G.
As the cells in our bodies divide and grow, the DNA in cells replicate easily and quickly as well. In DNA replication, the two inter-twined strands separate, and each is used as a template to form a new strand. Think of it as making a new zipper, but using one-half of the old zip as a model.
Cleaning Up The Mess!
The process of DNA replication is error prone. To make matters worse, exposure to harmful ultraviolet rays from the sun, or habits such as smoking can be harmful to cells and can damage the DNA. This led scientists to theorize that there had to be a way for cells to repair the new DNA that is formed; otherwise we would all be a big chemical mess!
Lindahl, Modrich and Sancar discovered repair enzymes that helps cells protect themselves. When new DNA strands are formed, every micro-inch of the new strand is inspected. These enzymes then snap off damaged bits of the new DNA strand, and replace it with the proper chemical pairs (A-T, C-G). People born with defects in this repair mechanism are prone to cancer.
Our human body never ceases to amaze us, isn't it!