termination reaction and a segment is gained when ddctp is utilized in the upstream termination reaction the observed sensitivity should parallel these theoretical values if shadow segments are not a major problem and all termination segments occur at reasonable intensities unmodified ddntps are not combined in one reaction because certain mutations would result in an absent and added base at the same site table 1 however when one of the dideoxy nucleotides is modified so that the mobility is changed by at least 1 bp all types of mutations can be detected in one reaction dnf 1r any modification that cause a discernable shift in the mobility of fragments containing the modified ddntp may be employed rox conjugated ddctp and fam conjugated ddatp retard the migration of dna segments by two nucleotides 8 while incorporation of biotin 11 dutp a commercially available analog of ttp causes a one nucleotide mobility shift 6 ideally a modified nucleotide would retard mobility by one and a half or two and a half nucleotides such that extra and absent segments due to the mutation are less likely to migrate identically to another segment e g hexyethylene oxide 0009 fig1 illustrates two embodiments of the denaturation fingerprinting method of this invention the figure illustrates the initial pcr amplification of a nucleic acid segment such as a genomic region of interest using primers a and b taq.