Shared Y chromosome repetitive DNA sequences in stallion and donkey as visualized using whole-genomic comparative hybridization

Abstract

The genome of stallion (Spanish breed) and donkey (Spanish endemic Zamorano-Leonés) were compared using whole comparative genomic in situ hybridization (W-CGH) technique, with special reference to the variability observed in the Y chromosome. Results show that these diverging genomes still share some highly repetitive DNA families localized in pericentromeric regions and, in the particular case of the Y chromosome, a sub-family of highly repeated DNA sequences, greatly expanded in the donkey genome, accounts for a large part of the chromatin in the stallion Y chromosome.

Figure 1

Panel 1a shows metaphase chromosomes of stallion after hybridization with an equimolar genomic DNA probe obtained using whole stallion (labelled in green) and donkey genomic DNA (labelled in red). Note that all autosomes reveal FISH signal corresponding to the stallion DNA labelling colour (green, see standard arrows), while red (donkey) is present in some autosomes (arrowhead) and the Y chromosome. A diagram showing the possible expansion and divergence among centromeric and pericentromeric DNA subfamilies is shown in panel b. Colour code for each species is maintained.