7994
Alleles of RPB1 ( RPO21 ) with elevated slippage rates were identified among 6 - azauracil - sensitive mutants and were also isolated using a slippage - dependent reporter gene .
 6 - azauracil
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 6 - azauracil