Some Aspects of Chromosome Structure and Functions
It was at the end of the 19th century that a Swiss biologist, Karl Nageli first proposed the existence of hereditary organelles that carried information from parent to offspring. Ensuing decades experienced vigorous studies that led to the development of
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Some Aspects of Chromosome Structure and Functions
Edited by
R.C. Sobti Department of Biotechnology Panjab University, Chandigarh, India
G.Obe Institute of Genetics University of Essen, Universitaetsstrasse 5, D-45117, Essen, Gennany
R.S. Athwal Department of Pathology and Laboratory Medicine Fels Institute for Cancer Research and Molecular Biology Temple University School of Medicine Philadelphia, USA
Kluwer Academic Publishers BOSTON
DORDRECHT
LONDON
,
Narosa Publishing House DELHI CHENNAI MUMBAI KOLKATA
A c.1.P. catalogue record for the book is available from the Library of Congress
ISBN 0-7923-7057-0
Copublished by Kluwer Academic Publishers, PO. Box 17, 3300 AA Drodrecht, The Netherlands with Narosa Publishing House, New Delhi 110 002, India Sold and distributed in North, Central and South America by Kluwer Academic Publishers, 101 Philip Drive, Norwell, MA 02061, U.S.A. and in Europe by Kluwer Academic Publishers, P.O. Box 322, 3300 AH Dordrecht, The Netherlands
In all other countries by Narosa Publishing House, 22 Daryaganj, Delhi Medical Association Road, New Delhi-I 10 002, India
All rights reserved Copyright © 2002, Narosa Publishing House, New Delhi, India No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner.
Dedicated to
Dr. Adayapalam T. Natarajan Professor Emeritus, Leiden University Leiden, The Netherlands
in recognition of his contributions to the fields of Cytogenetics, Radiation Genetics and Environmental Mutagenesis
Preface It was at the end of the 19th century that a Swiss biologist, Karl Nageli first proposed the existence of hereditary organelles that carried information from parent to offspring. Ensuing decades experienced vigorous studies that led to the development of discovery that chromosomes are indeed the carriers of genetic information. Subsequent studies, especially by Morgan and Bridges, established unequivocally the chromosome theory of inheritance. Today, the structure of chromosome is well established. At the physical level, eukaryotic chromosomes are composed of a single, linear, double helix of DNA. The elementary helical structure involves nucleosomes, comprised of histones around which the DNA is wrapped. A hierarchy of higher order helical structures of chromosomal architecture may possibly be responsible for the regulation of gene expression. The localized condensations of DNA constitute chromomeres. Uncoiled structures sometimes extending from chromomeres, which form loops, is the result of discontinuities in the regular coiling of the DNA in the chromosome. The focus of the current investigations in this area is on the molecular architecture of the chromosomes, where many aspects are still in process of being unravelled. A total of three billion nucleotide pairs, which correspond to approximately 30,000-50,000 genes, exist in
