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: Codon 344 is a key residue within the tetramerisation domain , and the amino acid substitution of a proline for a leucine is predicted to have profound implications for tetramerisation and potentially DNA binding .
### Output Text:
Codon 344 is a key residue within the tetramerisation domain , and the amino acid substitution of a proline for a leucine is predicted to have profound implications for tetramerisation and potentially DNA binding . 