Nucleic Acids Research, 2012, Vol. 40, Database issue D1027 Figure 2. Screenshots of the BGMUT web pages showing a partial list of alleles and a speciﬁc allele of the H blood group system. or the glycosyltransferase activity, shows that even though variation in common alleles occurs within the same sequence stretches that deﬁne the common epitopic regions (4), in rare alleles, changes that affect the sero- logical response are seen throughout the exons. The result- ing amino acid alterations may cause altered folding that interferes with epitope presentation or gives rise to new epitopes. As expected, phenotypes usually result from absence of an intact protein and are caused by nonsense mutations, insertions or deletions, or absence of the common epitope due to recombination. More generally, in the systems documented in the database, the phenotype reﬂects a particular sequence alteration be it the result of a single or multiple molecular events (e.g. the Rh neg, ABO O and MNS Sta alleles). Clearly, in contrast to many global studies, data presented in BGMUT allow to focus on DNA changes in a single gene and a closer look at its resulting alleles, to ask how they came about and to consider the properties of the resulting proteins. This knowledge will only expand as complete sequence content of variant alleles become more readily available. OTHER RESOURCES WITHIN BGMUT Besides the alleles of 30 human blood group systems, BGMUT also provides information on the systems them- selves (Figure 1). Such information includes that on a system’s genes, such as their sequences, chromosomal lo- cations and the functions of proteins encoded by them. Links to database records elsewhere, such as the Online