Origin and evolution of avian microchromosomesBurt D.W.
Department of Genomics and Bioinformatics, Roslin Institute, Roslin, Midlothian (United Kingdom)
Do you have an account?
- Rent for 48h to view
- Buy Cloud Access for unlimited viewing via different devices
- Synchronizing in the ReadCube Cloud
- Printing and saving restrictions apply
Rental: USD 8.50
Cloud: USD 20.00
Article / Publication Details
The origin of avian microchromosomes has long been the subject of much speculation and debate. Microchromosomes are a universal characteristic of all avian species and many reptilian karyotypes. The typical avian karyotype contains about 40 pairs of chromosomes and usually 30 pairs of small to tiny microchromosomes. This characteristic karyotype probably evolved 100–250 million years ago. Once the microchromosomes were thought to be a non-essential component of the avian genome. Recent work has shown that even though these chromosomes represent only 25% of the genome; they encode 50% of the genes. Contrary to popular belief, microchromosomes are present in a wide range of vertebrate classes, spanning 400–450 million years of evolutionary history. In this paper, comparative gene mapping between the genomes of chicken, human, mouse and zebrafish, has been used to investigate the origin and evolution of avian microchromosomes during this period. This analysis reveals evidence for four ancient syntenies conserved in fish, birds and mammals for over 400 million years. More than half, if not all, microchromosomes may represent ancestral syntenies and at least ten avian microchromosomes are the product of chromosome fission. Birds have one of the smallest genomes of any terrestrial vertebrate. This is likely to be the product of an evolutionary process that minimizes the DNA content (mostly through the number of repeats) and maximizes the recombination rate of microchromosomes. Through this process the properties (GC content, DNA and repeat content, gene density and recombination rate) of microchromosomes and macrochromosomes have diverged to create distinct chromosome types. An ancestral genome for birds likely had a small genome, low in repeats and a karyotype with microchromosomes. A “Fission–Fusion Model” of microchromosome evolution based on chromosome rearrangement and minimization of repeat content is discussed.
© 2002 S. Karger AG, Basel
Article / Publication Details
Copyright / Drug Dosage / DisclaimerCopyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.