( Then ( we ( ( ( composed ( ( our review ) ( of literature ) ) ) ( about ( ( ( ( ( ( ( ( ( ( ( cloning , ) ( genetic engineering ) ) , ) genes ) , ) DNA ) , ) chromosomes ) , ) and ) ( related ( ethical issues ) ) ) ) ) . ) ) )
(ROOT (S (RB Then) (NP (PRP we)) (VP (VBD composed) (NP (NP (PRP$ our) (NN review)) (PP (IN of) (NP (NN literature)))) (PP (IN about) (NP (NP (NN cloning)) (, ,) (NP (JJ genetic) (NN engineering)) (, ,) (NP (NNS genes)) (, ,) (NP (NNP DNA)) (, ,) (NP (NNS chromosomes)) (, ,) (CC and) (NP (JJ related) (JJ ethical) (NNS issues))))) (. .)))
Then we composed our review of literature about cloning, genetic engineering, genes, DNA, chromosomes, and related ethical issues.
(ROOT (S (NP (NNS Genes)) (VP (VBP are) (VP (VBN composed) (PP (IN of) (NP (NN dna))))) (. .)))
Genes are composed of dna.