892
For adaptive polymorphisms characterized by gene presence / absence ( P / A ) variation , underlying loci commonly show signatures of long - term balancing selection , with gene - presence and gene - absence alleles maintained as two divergent lineages .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None