1. The Union operation can only be used on two datasets from the same species.
2. The Intersection operation can be used for datasets within or across species. The intersection rules are:
If two chosen datasets are from the same organism, ERGR will use the gene ID to do intersection operation.
If two chosen datasets are from different organisms and one of them is from human, ERGR will use human genes as the reference. Genes in non-human dataset will be transformed to human orthologs to do intersection operation.
If the user selects two non-human datasets from different organisms, genes in both datasets will be transformed to human orthologs. The intersection results are based on human ortholog genes from the two datasets.