OMA groups are groups of protein sequences that are inferred to be related exclusively by speciation events. Consequently, there is at most one sequence per species in each OMA group. By convention, each sequence belongs to at most one OMA group.
For an alternative, more inclusive definition of orthologous groups, consider using hierarchical orthologous groups.
Search an OMA group
Export Marker Genes
OMA Groups are useful for species tree reconstruction. You can export a set of marker genes for a subset of species of your choice.