Understanding science: Deciphering our DNA

Children, you must have often heard people mention DNA, particularly the DNA tests conducted in case of violence, murder, bomb blast, etc., for identification of victims and suspects. These tests have almost replaced the fingerprinting methods. DNA, ever since the discovery of its helical structure in 1953 by J.D. Watson, F. Crick and M.H.F. Wilkins, has led to great achievements in the development of medical and agricultural sciences. Vision, taste, hearing and the thinking process in your brain as you read this article, or doing homework, solving mathematical problems, playing football or cricket, etc., all are based on DNA orchestration in an elaborated symphony within the body cells. Let's take an example of the group of cells in your tongue. They help you to feel the taste of food. How do these cells know that their role is to decipher taste instead of something else? This is done by the instructions already written and recorded in the DNA of the tongue cells. These instructions tell the cell what role it has to play in the tongue. DNA records a detailed set of plans, like the blueprint of a house. Let's now learn more about DNA. DNA stands for Deoxyribo Nucleic Acid. It is so named because it is found mainly in the nucleus of the cell. The main role of DNA is to store and accumulate the features, habits, traits, disposition and personality of mom and dad, and transfer to you and your siblings. What DNA is composed of? Let's first recollect that the English language has only 26 alphabets (A-Z). All books, dictionaries, encyclopaedia in this language revolve around these 26 alphabets. DNA has only four alphabets through which the entire life processes of not only humans, but all the living beings including plants, bacteria, viruses etc., have evolved. These alphabets are known as ATCG (Adenine, Thymine, Cytosine and Guanine) respectively. They form the composite structure of DNA. They are also called bases hung on sugar phosphate backbone. The DNA is in the form of a strand. You will find that it consists of few As, Ts, Cs and Gs . Thus, it is the different combination of ATCG that gives the sense of taste. Their different combinations determine the outlook, habits and habitats of all the creatures in the world. It is just like different combination of English alphabets that make different words. In the DNA, only three letters are required to make a word. This word is called amino acid — a component of protein. There are 20 amino acids in a living body required for life to carry on and they are all translated from the DNA for the performance of its function. When the different amino acids (or words for our better understanding) are arranged together, they form genes (sentences) and just as different arrangements of words result in different sentences, each gene has a different arrangement of amino acids. Genes order the cell to make proteins. These proteins enable a cell to perform functions, such as tell the taste of food, finally. This function is done in a trillionth time of a microsecond. The assemblages of ATCG are specific for specific functions and consist of copies of dad's and mom's eyes, hair and other features. This is called heredity. Heredity is the science of inheriting traits from parents to their children. A trait is a notable feature or quality in a person. Each of us has different traits that make us unique as a result of the combination of ATCG. Traits are passed from generation to generation. We, as a whole, are composed of cells. A cell is a functional unit of tissues and organs. All body organs starting from hair to toes are built on cells just like a wall which is built by bricks. The combination of ATCG of each organ is specific for its own functional requirements. They work as guided by their own respective DNA. The cells of the body have been collected and when counted by scientists, they found that they are at least one hundred trillion in number. The total number of DNA molecules in these cells, when combined together, is around three billion! Each cell contains a lot of DNA material. If you just pull out DNA from a single cell of any organ and stretch it, you would find that it is about two to three meters long! You can match this size with your car. Aren't you amazed? Imagine how it all fits in a cell whose own size is so small that it cannot be viewed by naked eyes! Well, it is done by a compact packaging system of chromosomes provided in every cell.