( ( ( The reason ) ( why ( ( ( sex-linked genes ) ( -LRB- ( traits -RRB- ) ) ) ( are ( inherited differently ) ) ) ) ) ( ( is ( ( because , ) ( ( unlike ( autosomal chromosomes ) ) ( , ( ( ( ( the cock ) and ) ( the hen ) ) ( ( do n't ) ( have ( similarly ( paired chromosomes ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN reason)) (SBAR (WHADVP (WRB why)) (S (NP (NP (JJ sex-linked) (NNS genes)) (PRN (-LRB- -LRB-) (NP (NNP traits)) (-RRB- -RRB-))) (VP (VBP are) (VP (VBN inherited) (ADVP (RB differently))))))) (VP (VBZ is) (SBAR (IN because) (, ,) (S (PP (IN unlike) (NP (JJ autosomal) (NNS chromosomes))) (, ,) (NP (NP (DT the) (NN cock)) (CC and) (NP (DT the) (NN hen))) (VP (VBP do) (RB n't) (VP (VB have) (VP (ADVP (RB similarly)) (VBN paired) (NP (NNS chromosomes)))))))) (. .)))
The reason why sex-linked genes (traits) are inherited differently is because, unlike autosomal chromosomes, the cock and the hen don't have similarly paired chromosomes.
(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))))))) (. .)))