Abstract: A method for analyzing the repair of DNA modifications and base mispairings as well as apurinic and apyrimidinic sites by DNA repair enzymes, comprising the following steps: contacting (a) single- or double-stranded DNA molecules which were covalently coupled to a solid-phase matrix carrying primary or secondary amino groups by reaction with a reactive squaric acid derivative, and which have modifications and/or base mispairings and/or apurinic or apyrimidinic sites, with (b) a composition containing DNA repair enzymes; and determining the elimination of the DNA modifications and/or base mispairings and/or apurinic or apyrimidinic sites. The DNA molecules are covalently coupled to the solid state matrix via a primary or secondary amino group incorporated in the DNA molecule at the 5′-end or at the 3′-end of the DNA or in the 2′-position of at least one deoxyribosyl residue.