My half-brother and I (from different fathers) have received AncestryDNA (autosomal) test results. I ran the raw data through a utility to identify shared strands. Because we have different (and unrelated) fathers, I expected the results for the Y-chromosome to be quite different, so was surprised when the entire chromosome was flagged as a shared strand (1 non-matching SNP treated as matching). I infer from this that there must be very little variation in the Y SNPs? Is this true? If so, is there a reference sequence for the 885 SNPs for which Ancestry provides test results?