Southern blot data showing DNA fragments that resist denaturation. Data is shown for Southern blots in which freshly prepared genomic DNAs were cut with the indicated restriction enzymes and processed as normal (‘a’ tracks), or heated for one minute in water at 100°C and snap cooled on ice prior to gel electrophoresis (‘b’ tracks), or similarly heated and cooled before restriction enzyme digestion and electrophoresis (‘c’ tracks). Arrow heads indicate the expected position of Southern blot bands. The ‘Control’ probe (PSCDBP, Table 1), which is from a genome region that gives consistently strong Illumina Infinium signals, produces no bands in any heated sample. In contrast, the ‘Test’ probe (CAPN10, Table 1), which originates from a genome region that tends to give weak Illumina Infinium signals, produces strong bands in all the tracks, indicating the detected genomic fragments are not effectively denatured by the conditions applied prior to running on the agarose gel. Equivalent results were produced for denaturation attempts involving heating at 37°C for 10 minutes in 0.32 M NaOH, followed by pH neutralisation (data not shown).