No abstract

No abstract

Karyotypic analysis of plaice, Pleuronectes platessa L., and cod, Gadus morhua L., revealed that the chromosome numbers in both species vary but that chromosome arm numbers (NF) stay constant. The C-, Q-and R-banding patterns also confirmed that the population of plaice studied shows Robertsonian polymorphism. The tendency of reduction in chromosome number in fishes suggests that Robertsonian fusions play a role in karyotype evolution in fishes.

No abstract

A new technique is described for simultaneous N-band and nucleoLus identification using acridine orange staining following incubation of chromosome squashes in 50 per cent formamide. This technique, together with silver deposition, has been used to clarify the chromosomal locations of N-bands and nucleolus organisers in the two locust species Schistocerca gregaria and Locusta migratoria. S. gregaria consistently shows interstitial nucleolus organisers in chromosomes L3 and M6 while L. migratoria has telomeric nucleolus organisers in L2 and M6 and an interstital nucleolus organiser in S9 close to the centromere. All nucleolus organisers also N-band and C-band but in addition both species have a large interstitial N-band on chromosome M8 which does not act as a nucleolus organiser. These data are discussed in relation to the mechanism of N-banding, the conflicting reports in the literature of different nucleolus organiser locations in these species and the significance of chromosome regions which N-band but do not act as nucleolus organisers.