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: By combining these oligos , we were able to amplify fragments from 100 to 300 bases ( b ) from mouse liver cDNA by polymerase chain reaction after reverse transcription ( RT - PCR ) .
### Output Text:
By combining these oligos , we were able to amplify fragments from 100 to 300 bases ( b ) from mouse liver cDNA by polymerase chain reaction after reverse transcription ( RT - PCR ) . 