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: To investigate the role of gene dosage in more detail , we have generated yeast artificial chromosome transgenic mice carrying the human PAX6 locus .
### Output Text:
To investigate the role of gene dosage in more detail , we have generated yeast artificial chromosome transgenic mice carrying the human PAX6 locus . 