( Alleles - )
(ROOT (NP (NNS Alleles) (: -)))
Alleles -
(ROOT (S (NP (NNP Allele)) (ADVP (RB frequecy)) (VP (VBZ is) (NP (NP (DT the) (NN rate)) (SBAR (WHPP (IN at) (WHNP (WDT which))) (S (NP (DT a) (JJ specific) (NN allele)) (VP (VBZ appears) (PP (IN within) (NP (DT a) (NN population)))))))) (. .)))