2833
Interestingly , these " activation - defective " mutants segregated into two classes : 1 ) those that were unable to form dimers but that could still form higher order oligomers and transform cells , and 2 ) those that were defective for PDGF - R binding and were transformation - incompetent .
 GENE: PDGF - R
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 GENE: PDGF - R