This invention provides a transgenic mouse for studying the role of senescent cells on an age-related disorder or an age-sensitive trait. The transgene contains a p16 promoter sequence that controls expression of an enzyme so as to cause the enzyme to be expressed in senescent cells in the mouse. The enzyme converts a prodrug to a cytotoxic agent, so that treating the mouse with the prodrug results in the prodrug selectively killing the senescent cells. As a result, progression of an age-related disorder or an age-sensitive trait is delayed. Included is the 3MR mouse model, which also expresses bioluminescent and fluorescent markers under control of the p16 promoter so that senescent cells in the mice can be visualized.