The process whereby a single cell, the fertilized egg, develops into an
adult has fascinated for centuries. Great progress in understanding that
process, h- ever, has been made in the last two decades, when the
techniques of molecular biology have become available to developmental
biologists. By applying these techniques, the exact nature of many of
the interactions responsible for forming the body pattern are now being
revealed in detail. Such studies are a large, and it seems
ever-expanding, part of most life-science groups. It is at newcomers to
this field that this book is primarily aimed. A number of different
plants and animals serve as common model org- isms for developmental
studies. In Molecular Methods in Developmental Bi- ogy: Xenopus and
Zebrafish, a range of the molecular methods applicable to two of these
organisms are described, these are the South African clawed frog,
Xenopus laevis, and the zebrafish, Brachydanio rerio. The embryos of
both of these species develop rapidly and externally, making them
particularly suited to investigations of early vertebrate development.
However, both Xenopus and zebrafish have their own advantages and
disadvantages. Xenopus have large, robust embryos that can be
manipulated surgically with ease, but their pseudotetraploidy and long
generation time make them unsuitable candidates for genetics. This
disadvantage may soon be overcome by using the diploid Xenopus
tropicalis, and early experiments are already underway. The transp- ent
embryos of zebrafish render them well-suited for in situ hybridization
and immunohistochemistry, and good for observing mutations in genetic
screens.
