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In transformed E . coli , constitutive CAT expression is maintained when as little as 0 . 3 kilobase of DNA from the 3 ' end of the 1 . 6 - kilobase segment is inserted in the correct orientation in front of the CAT gene .
 constitutive CAT, CAT gene
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 constitutive CAT, CAT gene