A collection of polymorphic DNA sequences has been used to analyse the
variability of a panel of 91 Y chromosomes. Some sequences (DYZ1 and
DYZ2) were highly polymorphic and allowed all of the chromosomes to be
distinguished. Other sequences were less polymorphic and were used to
construct a haplotype for each chromosome and to assign chromosomes t
o groups. The best understood of these loci could be used to construct
a tree showing the evolutionary relationships between the groups of Y
chromosomes. In general, Y chromosomes from different ethnic backgrou
nds belong to different groups.