11994
Anal fins were used for qualitative gene expression analysis of the genes sonic hedgehog ( shh ) , muscle segment homeobox C ( msxC ) , and fibroblast growth factor receptor 1 ( fgfr1 ) by in situ hybridization .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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