( ( Traits ( controlled ( by ( alleles ( on ( sex chromosomes ) ) ) ) ) ) ( ( are sex-linked ) . ) )
(ROOT (S (NP (NP (NNS Traits)) (VP (VBN controlled) (PP (IN by) (NP (NP (NNS alleles)) (PP (IN on) (NP (NN sex) (NNS chromosomes))))))) (VP (VBP are) (ADJP (JJ sex-linked))) (. .)))
Traits controlled by alleles on sex chromosomes are sex-linked.
(ROOT (S (NP (JJ Sex-linked) (NNS traits)) (VP (VBP are) (VP (VBN located) (PP (IN on) (NP (NP (NNS genes)) (PP (IN on) (NP (NN sex) (NNS chromosomes))))))) (. .)))