2610
The sequence analysis of both products of individual phi 80 site - specific recombination events in vivo shows that recombination with a secondary attachment ( att ) site generates several different novel joints at the mismatched position : one recombination event resulted in a single base - pair deletion and two other recombination events resulted in two different single base - pair substitutions .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 None