2612
Temperature - shift experiments using synchronously grown cells of a delta top1 top2 temperature - sensitive ( ts ) double mutant and its isogenic top2 ts strain show that , whereas mitotic blocks can prevent killing of the top2 ts mutant at a nonpermissive temperature , the same treatments are ineffective in preventing cell death of the delta top1 top2 ts double mutant .
 delta top1, top2 temperature - sensitive ( ts ) double mutant, top2, top2 ts mutant, delta top1, top2 ts double mutant
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 delta top1, top2 temperature - sensitive ( ts ) double mutant, top2, top2 ts mutant, delta top1, top2 ts double mutant