Fundamentals of Cell and Molecular Genetics
Arvind K. Misra Department of Botany, North-Eastern Hill University, Shillong 793022
Panima Publishing Corporation New Delhi / Bangalore
Copyright (C) Panima Publishing Corp New Delhi, 2011
All rights reserved. No Part of this publication may be reproduced or transmitted in any form or by any means without the written permission of the publishers.
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Preface The book in your hands is a product of my interaction with students over a period of thirty years. I have learnt during the process of teaching. I have modelled the book in a notes mode and too many experimental details and scientific evidences have been deliberately kept out. I want this book to serve the students only as a book dedicated to fundamental concepts. This book would be useful for both undergraduate and postgraduate students preparing for basic sciences and biotechnology, including those preparing for NET examinations. I have taken little assistance from others. Nevertheless, many things in the book are based on study material collected/generated by me from time to time. Consequently, I would like to thank many fellow workers whose writings have helped me understand the vastness of genetics. The book may have several errors, some inadvertent and others due to ignorance. I solicit comments from all readers so that I am able to improve up on this work. I dedicate this work to my parents, my first teachers.
Prologue I am often confronted with the dilemma of defining life. I know it has taken generations of brilliant scientists and philosophers without any tangible resolution of the dilemma. Life has been dissected to the smallest molecules. Yet when you mix these molecules in the right proportion, life is not created. Salt of Deoxyribose Nucleic Acid (DNA) may be precipitated and in dried form it is like any other chemical powder. Yet the same DNA when put within the confines of a cell starts doing things that are expected of a living entity. We can now create conditions in a test tube where the DNA would start replicating. Have we created life? No. Then what is this change that makes a DNA „living‟ within a cell and „dead‟ outside of it? It is a difficult question. I do not have any precise answer to this. However, in my opinion „life‟ is certainly not just a collection of some bio-molecules; it is an ordered interaction among these bio-molecules. It is now in the realm of household knowledge that Mendel‟s initial work with pea plant opened up avenues for human insight into nature‟s way of perpetuating and inheriting basic information required for ordered functioning of life forms. Man has always wondered at the huge variety of life forms on earth and often thought each life form to be a water tight compartment, following its own rules. The enormous amount of scientific information generated since later part of twentieth century has made us realize the similarity of different life forms. We now have two distinct approaches in our quest for unravelling life. The first approach looks at commonality of lif