( ( In ( ( humans and ) ( other ( mammal species ) ) ) ) ( , ( sex ( ( is ( determined ( by ( ( two ( sex chromosomes ) ) ( called ( ( ( the ( X chromosome ) ) and ) ( the ( Y chromosome ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NP (NNS humans)) (CC and) (NP (JJ other) (NN mammal) (NNS species)))) (, ,) (NP (NN sex)) (VP (VBZ is) (VP (VBN determined) (PP (IN by) (NP (NP (CD two) (NN sex) (NNS chromosomes)) (VP (VBN called) (NP (NP (DT the) (NNP X) (NN chromosome)) (CC and) (NP (DT the) (NNP Y) (NN chromosome)))))))) (. .)))
In humans and other mammal species, sex is determined by two sex chromosomes called the X chromosome and the Y chromosome.
(ROOT (S (NP (NNP Mammalian) (NN sex) (NN determination)) (VP (VBZ is) (ADJP (VBN determined) (RB genetically) (PP (IN by) (NP (NP (DT the) (NN presence)) (PP (IN of) (NP (NP (NNS chromosomes)) (VP (VBN identified) (PP (IN by) (NP (NP (DT the) (NNS letters)) (UCP (NP (SYM x)) (CC and) (ADJP (JJ y.))))))))))))))
Mammalian sex determination is determined genetically by the presence of chromosomes identified by the letters x and y.