Animal cytogenetics

The contribution of Orthopteran material to our general understanding of the chromosome and cytogenetics has always been significant. From just after the rediscovery of Mendel? s work in the early part of the 20th Century, the large size of the chromosomes and low numbers in the complements of most species have caused investigators to turn again and again to this group as their experimental material. In 1951 White reviewed the important areas where the Orthoptera had furnished evidence, from the pioneer work of McClung (1905) to the then present. Many of the same issues are still with us today albeit in a somewhat different guise, for a series of revolutions in biology in the last 25 years has greatly expanded our understanding of the chromosome, including that most fundamental series of discoveries that established DNA as the genetic material. Chromosome structure, replication, transcription, movement, pairing, chiasma formation and mutation are fields of great activity at present, and it was initially intended to include sections on these topics. But whilst the Orthoptera can contribute much to these debates, they are general phenomena which properly require a consideration of evidence from many groups of organisms besides the Orthoptera. Furthermore the Orthoptera do not appear to differ greatly from other groups in the general outline of these features Consequently only those aspects where Orthopteran material is particularly relevant will be mentioned and they will be dealt with in the context of chromosomal variation and evolution in the Orthoptera.