Nucleic Acid Hybridization In The Study Of Cell Differentiation

The informational content of cells is encoded in the nucleotide sequences of their DNA. The restrictions on base pairing- A pairing with T (U), and G pairing with C - in nature assures the fidelity of replication of DNA in cell division, and of transcription. In the test tube, these restrictions can be exploited for ascertaining similarities and dissimilarities of nucleic acids of varying origin by measuring the kinetics of reassociation of polynucleotides to double-stranded molecules in DNA DNA renaturation or RNA-DNA hybridization experiments, and by determining the thermal stability and other physical-chemical properties of the resulting hybrid molecules. This method has enormous potential for developmental biology. It offers a more direct approach to the ever-present question of the genetic identity of different cell types in an individual organism, and a more direct test of the hypothesis of diffe rential gene function. It offers the possibility of localizing genes on chromosomes without the use of Mendelian genetics. It is an indispensable tool in the isolation, purification, and characterization of genes. This volume brings together six articles by investigators actively working on various aspects of developmental biology who use nucleic acid hybridization as a tool in their research. Sound in theory, the method is in a honing phase as regards the technical detail. This is expressed in the hesitation with which some of the conclusions are rightly drawn.

This book examines the theory behind nucleic acid hybridization, presenting a variety of basic protocols. Methods are provided for the use of standard techniques, including filter and liquid hybridization. Important applications of hybridization such as PCR and its uses in genetic fingerprinting are also covered. 80 illus.

It is instructive to compare the response of biologists to the two themes that comprise the title of this volume. The concept of the cell cycle-in contra distinction to cell division-is a relatively recent one. Nevertheless biologists of all persuasions appreciate and readily agree on the central problems in this area. Issues ranging from mechanisms that initiate and integrate the synthesis of chro mosomal proteins and DNA during S-phase of mitosis to the manner in which assembly of microtubules and their interactions lead to the segregation of metaphase chromosomes are readily followed by botanists and zoologists, as well as by cell and molecular biologists. These problems are crisp and well-defined. The current state of "cell differentiation" stands in sharp contrast. This, one of the oldest problems in experimental biology, almost defies definition today. The difficulties arise not only from a lack of pertinent information on the regulatory mechanisms, but also from conflicting basic concepts in this field. One of the ways in which this situation might be improved would be to find a broader experimental basis, including a better understanding of the relationship between the cell cycle and cell differentiation.