( ( Types ( of mutagens ) ) ( ( include ( ( ( ( ( radiation , ) chemicals ) , ) and ) ( infectious agents ) ) ) . ) )
(ROOT (S (NP (NP (NNS Types)) (PP (IN of) (NP (NNS mutagens)))) (VP (VBP include) (NP (NP (NN radiation)) (, ,) (NP (NNS chemicals)) (, ,) (CC and) (NP (JJ infectious) (NNS agents)))) (. .)))
Types of mutagens include  radiation, chemicals, and infectious agents.
(ROOT (S (NP (NP (NNP Radiation)) (, ,) (NP (NNS chemicals)) (, ,) (CC and) (NP (JJ infectious) (NNS agents))) (VP (VBP are) (NP (NP (NNS types)) (PP (IN of) (NP (NNS mutagens))))) (. .)))