TABLE 1.

Genotoxic Endpoints and Definitions

Endpoint	Definition
Chromosomal damage	Chromosomal alterations (i.e., coding properties) that occur during division of cells
DNA methylation	Addition of methyl group to cytosine (5’-CpG-3’)
DNA–protein cross-linking	Chemically activated trapping of proteins on DNA strands
Micronuclei formation	Fragments of chromosomal matter outside the nucleus
Sister-chromatid exchange	Exchange of genetic material between two identical copies of the same chromosome
DNA repair inhibition	Inhibition of the natural process of repairing a harmful DNA lesion
Gene mutation	Alteration of DNA or nucleotide sequence of one or more genes
Chromosomal aberrations	Changes in chromosome number or structure
DNA fragmentation	Rapid separation or breaking of DNA strands into pieces
DNA strand breaks	Single- or double-break of the DNA sequence in the genetic material
Telomere alteration	Change in the noncoding ends of the DNA that serves to protect the coding portion

Note. Endpoints are listed in hierarchical order from less to more permanent gene damage.