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Within DNA trinucleotide repeat sequences , the repair of DNA damage by the processes of homologous recombination , non-homologous end joining , DNA mismatch repair or base excision repair may involve strand slippage mispairing leading to trinucleotide repeat expansion when the repair is completed .
 trinucleotide repeat expansion
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 trinucleotide repeat expansion