In the sentence extracted from biomedical literature, identify all the disease entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="disease"> to denote a disease.

### Input Text: We show that this region of the genome contains a tandem duplication of approximately 30 kilobases , which results in two copies of BRCA1 exons 1 and 2 , of exons 1 and 3 of the adjacent 1A1 - 3B gene and of the previously reported 295 base pair intergenic region .
### Output Text:
We show that this region of the genome contains a tandem duplication of approximately 30 kilobases , which results in two copies of BRCA1 exons 1 and 2 , of exons 1 and 3 of the adjacent 1A1 - 3B gene and of the previously reported 295 base pair intergenic region . 