19371
Although marapsins are type I transmembrane proteins in their typical form , they mutated independently into anchorless forms in several mammalian clades , including one involving humans .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None