Genetics and Molecular Biology S E C O N D E D I T I O N Robert Schleif Department of Biology The Johns Hopkins University Baltimore, Maryland The Johns Hopkins University Press Baltimore and London 1986 by Addison-Wesley Publishing Company 1993 by Robert Schleif All rights reserved Printed in the United States of America on acid-free paper The Johns Hopkins University Press 2715 North Charles Street Baltimore, Maryland 21218-4319 The Johns Hopkins Press Ltd., London ...