Primer selection
To select the primers used, sequences of the HO gene
regions were downloaded from the NCBI nucleotide database
and aligned using the multiple sequence alignment
program clustal_x (1Æ8) (Thompson et al. 1997). Based
on these alignments, the S. cerevisiae ⁄ S. pastorianus
(ScHO-F and ScHO-R)- and S. bayanus ⁄ S. pastorianus
(LgHO-F ⁄ LgHO-R)-specific primers were designed
(Table 2). The specificity of these primers was verified by
searching for homologous nucleotide sequences in the
GenBank sequence database using the blast search
program (http://www.ncbi.nlm.nih.gov/).