Fig. 2. ichabod maps near the ß-catenin-2 locus in the telomeric region of LG19. (A) Linkage map of the distal region of LG19 obtained from a map cross of an ichabod female and brass male (see text for description). Map positions (in cM) are obtained from the latest update of the integrated map of the zebrafish genome (see Day et al. at http://zfin.org). Two markers were tested for map position 91.5 cM (z68894/z24777) and for map position 91.6 (z1799/CA91.6-1) and single markers were tested at other map positions. Recombination frequencies (recombinants/meiosis tested) between ichabod and each of the markers are shown below the map. In addition to testing SSLP markers from the MGH microsatellite map (`Z' markers), we tested two additional markers: (1) CA85.6-3, a polymorphic CA-repeat marker located 1.5 kb from the non-polymorphic marker, Z26695, previously mapped to position 85.6 cM on LG19; and (2) CA(91.6)-1, a polymorphic CA-repeat marker found within the 3'UTR of ß-catenin-2 cDNA [an EST for ß-catenin-2, fc16f05/mgc:65770 had previously been mapped to 91.6 on the heat shock meiotic panel by Ian Woods and William Talbot (unpublished)]. The closest marker showing recombination with ichabod was CA(85.6)-3, located 1.1 cM away. No recombinants were obtained between ichabod and z68894, z24777, CA(91.6)-1, z1799, z25291 and z61401, even though these markers were spread over a region extending almost 10 cM from CA(85.6)-3. (B) Linkage map of SSLP markers determined from a completely independent map cross (generated from a WIK x OregonAB/TübingenWT cross). To test if the map positions in the non-recombinant region of the map cross shown in A were correct, we determined recombination frequencies using markers that spanned this region. As is indicated, in contrast to the ichabod map cross, we did observe recombination in this region of LG19 (except between markers z14236 and z25291).