Isolation and Genomic Analysis of the Cetacean Y-chromosome

The male-specific mammalian Y-chromosome represents a powerful tool for studying malemediated gene flow and genome evolution. Here it was possible to identify 7 polymorphic microsatellites for the first time in an odontocete species, using a combination of cell culture, cytogenetics and molecular approaches. Initially, the development of an efficient and repeatable methodology for obtaining a growing lymphocyte culture that facilitated the isolation of individual chromosomes is described. Flow karyotypic characterization and isolation of individual chromosomes via flow sorting or microdissection is reported for the killer whale (Orcinus orca). Microdissected Y-chromosomes from the killer whale and bottlenose dolphin (Tursiops truncatus) were screened for sequences containing microsatellite motifs. 15 and 10 male-specific microsatellites were identified from the killer whale and bottlenose dolphin, respectively. Additional microsatellite loci were identified from previously published fin whale Y-chromosome sequence. 6 markers designed from heterologous sequences amplified from sperm whales (Physeter macrocephalus), were also screened for variation. All 31 markers were monomorphic in the bottlenose dolphin, only 2 loci showed 2 variants in the killer whale and 7 were polymorphic in the sperm whale. In addition 162 anonymous regions of the Y-chromosome, isolated from the delphinid species were used to characterize the comparative composition of the ‘Y’ relative to the autosomes in these species. Characteristics are discussed in the context of the genome as a whole, species-specific history and with reference to the expected patterns of mammalian Y-chromosome evolution.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

Durham University

Year dc:date.issued

2010

Author dc:creator

• Elliott, Vittoria Louise