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44 || AWSAR Awarded Popular Science Stories - 2019
matter), else it will simply skip the chapter. TFs can then be likened to “bookmarks.” But, these are no ordinary bookmarks. If the TFs fail to bookmark an important chapter in our genome book, we could
land up in serious diseased states, often leading to death. In fact, one-third of all human diseases, including cancers and neurological diseases, are caused by TFs that fail to bookmark an important gene or land up bookmarking a wrong gene.
Looking for the code.
The entire process of reading
a gene described above is
called transcription. Each gene
is made up of large strings of
DNA, just like each chapter is
made up of sentences. And,
just as each sentence is made
up of a maximum of 26 letters,
DNA is made up of 4 letters A, T, G, and C. These four letters actually denote four different chemical groups. The entire promoter region (introduction section) is a long sentence of DNA (there are no punctuation marks in DNA) as shown in the illustration below. There are thousands of TFs in our body, each with an assigned task of bookmarking a particular set of gene chapters. To identify the chapter, it needs to bookmark; the TF looks for a unique code word, which is about 8–10 letters long, in the extremely long string of DNA sentence in the introduction section. If it finds the code, it bookmarks that chapter for the RNA polymerase to read through it.
The code confusion. For several years, scientists believed that this process was simple; a TF read through each chapter, found its code and bookmarked it, or did not find the code and skipped it. However, further research revealed that some TFs found the
code that they were looking for and yet did not bookmark that chapter. Other TFs identified codes that did not exactly match with the code they were meant to bind to, and yet, landed up
bookmarking that chapter. Yet other TFs identified a certain code when they were alone, but when they were reading the introduction along with other TFs, they identified completely new codes. This situation was just too confusing, and something had to be done to demystify the decoding strategy of TFs as without identifying their decoding strategy, it was impossible to treat TF-related diseases.
Decoding the code.
Several scientists across the world set out on a venture to decode the TF code. Their experimental strategy, called
deep sequencing, involved extracting the genome from different organisms and letting the entire bunch of TFs bookmark whichever gene they wanted to. And, then they extracted
THE GENOME BOOK AND THE CODE CONFUSION
We are quite right when we claim our DNA to be special because each one of us carries a unique set of DNA. This entire set of DNA put together can be likened to a book called the genome. Our unique genome makes us who we are. My genome book is made of individual chapters called genes, with chapter titles such as dance, cooking, anger, brown eyes, sleepyhead, and so on.