( ( Genes ( on ( the ( sex chromosomes ) ) ) ) ( ( are ( called ( sex-linked genes ) ) ) . ) )
(ROOT (S (NP (NP (NNS Genes)) (PP (IN on) (NP (DT the) (NN sex) (NNS chromosomes)))) (VP (VBP are) (VP (VBN called) (NP (JJ sex-linked) (NNS genes)))) (. .)))
Genes on the sex chromosomes are called sex-linked genes.
(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))))))) (. .)))