The sequence alignment and the conserved elements of the control region of one individual of each, the willow (II), great (III) and blue (IV) tits, are shown in figure 3. In addition, the Siberian tit, a close relative to the willow tit, was included in the alignment.
The length of the control region was quite constant between the species studied: 1205-1207 bp in willow tit (25 birds), 1188-1189 bp in great tit (68 birds) and 1191 bp in blue tit (43 birds). Most of the insertions or deletions causing length differences between the species are located within the third domain of the control region. This portion of the control region seems to be quite free from functional constraints and has very low similarity among the species.
Conserved elements were identified on the basis of sequence similarity with other vertebrate sequences (Yoneyama 1987, Southern et al. 1988, Desjardins & Morais 1990 and 1991, Suzuki et al. 1991, Quinn & Wilson 1993, Janke et al. 1996, Marshall & Baker 1997). The first domain contained a C-stretch, which is located near to the 5’ end of the control region and is identical among the tit species studied. A possible TAS element, identified on the basis of the consensus sequence from eleven vertebrate species aligned by Foran et al. (1988), was also located in the first domain.
Most of the conservative boxes were within the second domain (F-, E-, D-, C- and B-boxes and part of the CSB-1). The E-box showed the least amount of sequence similarity (55 %). The other boxes had 83-96 % similarity over the four species. The CSB-1, beginning at the end of the second domain and ending at the third domain, contained an insertion that is also found in some other Passerines (e. g. in the common chaffinch, Fringilla coelebs). This insertion has 85 % similarity with an avian infectious bronchitis virus (Penzes et al. 1994).