Željka Pezer: Sex determination in some Cetacean
species by the polymerase chain reaction. Diploma Thesis.
Faculty of Science.
Abstract
Investigations of cetacean biology often encounter
problems in gaining information from the field. It is not always possible to
morphologically determine sex of an animal whose carcass was found in an
advanced state of decomposition. Determining the gender of living cetaceans is
also difficult or impossible, since in most species sexually dimorphic
characters are poorly marked. The purpose of this study was to introduce a
reliable method for molecular sexing of cetaceans that could be used on tissue
samples from carcasses, as well as on skin biopsies from living animals. Total
DNA was extracted from muscle tissue of 49 cetacean specimens; 27 bottlenose
dolphins (Tursiops tmncatus\ 11 striped dolphins (Stenella
coeruleoalba\ 7 Risso's dolphins (Grampus griseus), 2 Cuvier's
beaked whales (Ziphius cavirostris) i 2 fin whales (Ba/aenoptera
physalus). In one case DNA was extracted from skin. All samples were taken
from corpses in different state of decomposition. The introduced method uses
polymerase chain reaction (PCR) to amplify regions on ZFY and ZFX, which are
the homologous genes located on Y- and X-chromosomes, respectively. Three
oligonucleotide primers were employed to produce fragments specific for the ZFY
and ZFX sequences. Amplification products differed in length and therefore gave
distinct, sex-specific bands on 1% agarose gel after electrophoresis. The sex
of 40 cetacean specimens was successfully determined. Method tailed in cases of
strongly decomposed tissues, but was shown to be reliable and efficient when
applied on fresh or well preserved samples.