Identification and analysis of sex chromosomes by comparative genomic hybridization (CGH).

Comparative Genome Hybridization (CGH) can be used as a universal method for the identification of molecularly differentiated sex chromosomes. This is profitable in species with homomorphic sex chromosomes or when chromosomes are unfavourable for cytogenetics, e.g. when size differences are insufficient, chromosomes numerous and/or banding methods fail. In this method, genomic DNA from females competes as a probe with that from males for binding to the chromosome targets. Easy extraction and labelling methods afford a method that can be applied even when few specimens are available, e.g. when specimens for investigation have to be collected in the field - CGH also offers the possibility to obtain a rough estimate of the DNA composition of the sex chromosome.