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However , electron microscopy revealed that while sec4 mutant cells accumulate secretory vesicles , ypt31 / 32 mutant cells accumulate aberrant Golgi structures .
 GENE: sec4 mutant; GENE: ypt31 / 32 mutant
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: sec4 mutant; GENE: ypt31 / 32 mutant