( Alleles ( ( can ( be ( ( ( ( ( ( dominant alleles ) , ) ( which ( always ( win out ) ) ) ) , ) or ) ( ( ( recessive alleles ) , ) ( which ( are ( masked ( in ( ( the presence ) ( of ( a ( dominant allele ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Alleles)) (VP (MD can) (VP (VB be) (NP (NP (NP (JJ dominant) (NNS alleles)) (, ,) (SBAR (WHNP (WDT which)) (S (ADVP (RB always)) (VP (VBP win) (PRT (RP out)))))) (, ,) (CC or) (NP (NP (JJ recessive) (NNS alleles)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBP are) (VP (VBN masked) (PP (IN in) (NP (NP (DT the) (NN presence)) (PP (IN of) (NP (DT a) (JJ dominant) (NN allele))))))))))))) (. .)))
Alleles can be dominant alleles, which always win out, or recessive alleles, which are masked in the presence of a dominant allele.
(ROOT (S (NP (NP (DT An) (NN allele)) (SBAR (WHNP (WDT that)) (S (VP (VBZ 's) (ADVP (RB always)) (VP (VBN expressed) (PP (IN over) (NP (DT another)))))))) (VP (VBZ is) (NP (DT a) (JJ dominant) (NN allele))) (. .)))