Double-strand dna break quantification method

A method for quantifying double-stand breaks in a sample comprising DNA molecules susceptible of having at least one DNA nick, at least one DNA gap and at least one DNA double strand break, the method comprising:

• (a) contacting the sample with a DNA ligase and a DNA polymerase under conditions to (i) allow the reparation of the at least one DNA nick and the at least one DNA gap, (ii) inhibit the amplification of the DNA molecules and (iii) obtain a first DNA mixture comprising a first DNA molecule having a 3′-OH free terminus;
• (b) contacting the first DNA mixture with a terminal deoxynucleotidyl transferase (TdT) and a substrate of the TdT, said substrate comprising a nucleotide having a label, under conditions so as to allow the incorporation of the nucleotide at the 3′-OH free terminus of the first DNA molecule to obtain a second DNA mixture comprising second DNA molecules having the incorporated nucleotide;
• (c) purifying the second DNA molecules from the second DNA mixture to obtain at substantially isolated DNA molecules;
• (d) optionally amplifying, arraying and/or sequencing the substantially isolated DNA molecules obtained at step (c);
• and
• (e) quantifying a signal associated with the substantially isolated DNA molecules obtained at step (c), the amplification of the substantially isolated DNA molecules obtained at step (d), the array of the substantially isolated DNA molecules obtained at step (d) and/or the sequence of the substantially isolated DNA molecules obtained at step (d) to quantify and optionally locate DNA double-strand breaks in the sample.