DNA fingerprinting and minisatellite variation of swans
Genetic variation in natural populations of four species of swans (Cygnus bewickii, Cygnus olor, Cygnus buccinator and Cygnus cygnus) has been investigated by examining minisatellite loci using human DNA fingerprinting probes pSPT19.6 and pSPT18.15. It has been found that swan minisatellites are highly variable. However, the degree of variation depends on the population structure and species. Bewick's Swans at Slimbridge have the highest degree of minisatellite variation, Whooper Swans at Caerlaverock come second, and then Mute Swans, and Trumpeter Swans in Montana. Comparative study of DNA fingerprints among populations and among species suggested that swan minisatellites are subject to specific as well as population differentiation, although the function of minisatellites remains an unsolved mystery. Hypervariable minisatellites of swans that are detected by DNA fingerprinting are stably inherited as codominant markers. DNA fingerprinting has been used to study mating behaviour of Mute and Whooper Swans in the wild The results showed that the Whooper swans were almost strictly monogamous and Mute Swans exhibited an adaptable reproductive system. A genomic library from Cygnus olor was constructed and dozens of minisatellites were isolated. Most of the cloned swan minisatellites were variable, some showed specific variation, and one (pcoMS6.1) detected RFLPs in PstI digests of Trumpeter Swans.