Detection of Specific Sequences among DNA Fragments Separated by Gel Electrophoresis
Journal of Molecular Biology, 1975 · paper · Biomedicine
Describes a method for transferring DNA fragments from agarose gels to cellulose nitrate filters, then hybridizing them to radioactive RNA to detect specific sequences. It is illustrated with ribosomal RNA-complementary fragments from E. coli, Xenopus laevis and mammals.
Checked: PDF from gwern.net, fetched 5 Oct 2026. Page numbers are those of that PDF.
2 findings
Reference or label Fig. 6 legend refers to itself: "Hybridization and subsequent treatment of the filters was carried out as described in the legend to Fig. 6 and filters removed at the times indicated"; the procedure is in the legend to Fig. 5.
- p. 12 Fig. 6 legend
was carried out as described in the legend to Fig. 6 and filters removed at the times indicated
- p. 12 Fig. 6 legend
carried out as described in the legend to Fig. 6 and filters removed at the times indicated
- p. 12 Fig. 6 legend
carried out as described in the legend to Fig. 6
- p. 12
carried out as described in the legend to Fig. 6 and filters removed
Judge's note: Page 12 image clearly prints "in the legend to Fig. 6" inside the Fig. 6 legend. That legend contains no hybridization or washing details. The Fig. 5 legend on the same page gives them (6 × SSC, 2 × SSC wash, RNAase A treatment, drying, counting), and the first sentence of the Fig. 6 legend already cites Fig. 5 for filter loading. The pointer should read Fig. 5.
Second check: another model agreed
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Wording Materials state "32P-labelled rat DNA was a gift of M. S. Campo", but no experiment uses labelled rat DNA; sections (i) and (j) use "28 S RNA prepared from rat myoblasts labelled with 32P" and "32P-labelled rat 28 S RNA", whose source is not given, so "DNA" is probably a slip for "RNA".
- p. 2 Section (b), second paragraph
P-labelled rat DNA was a gift of M. S. Campo
- p. 15 Section (i), first paragraph
28 S RNA prepared from rat myoblasts labelled with
- p. 16 Section (j)
P-labelled rat 28 S RNA
- p. 2
82P-labelhd rat DNA was a gift of M. S. Campo
Only the authors can say what is right here.
Judge's note: Page 2 image prints "32P-labelled rat DNA was a gift of M. S. Campo" (the text layer's "82P-labelhd" is OCR noise). A text search finds no use of labelled rat DNA; the only rat DNA used is unlabelled liver DNA (gift of A. R. Mitchell). Pages 15 and 16 use 32P-labelled rat 18 S and 28 S RNA with no source stated in Materials. A slip for RNA is likely, but only the author can say. The reviewer's separate point about a missing preparation for 32P E. coli DNA is an omission, not an error, and is not part of this verdict.
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5 minor (typos and the like; most checked by the judge only)
Wording The requirements list gives "Three pieces of glass or Perspex, 5 cm × 20 cm and the same thickness as the gel", but the transfer procedure places only two ("One of the glass or Perspex sheets ... The second glass or Perspex sheet") and Fig. 1(a) shows two Perspex sheets.
- p. 3 Section (c), list of materials
Three pieces of glass or Perspex, 5 cm × 20 cm and the same thickness as the gel.
- p. 3 Section (c), transfer procedure
The second glass or Perspex sheet is laid 2 to 3 mm away from the other side of the gel (Fig. 1(a))
- p. 4 Fig. 1(a)
Perspex
- p. 3 Transfer procedure
The second glass or Perspex sheet is laid 2 to 3 mm away from the other side of the gel
Only the authors can say what is right here.
Judge's note: Page 3 image confirms the list says "Three pieces" and the procedure describes only a first and a second sheet, one on each side of the gel, bridging "the two air spaces". Fig. 1(a) on page 4 labels two Perspex sheets. No use of a third piece is described anywhere; the glass plate used as a weight appears only in the Fig. 2 legend for cylindrical gels. It could be a spare or an unstated use, so this is a query for the author.
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Wording Text says of "2 × SSC, 40% formamide at 40°C" that "this solvent removed DNA from the filters (see later section)", but the only formamide data later in the paper (Table 2) are for "6 × SSC in 50% formamide" at 50°C and 65°C.
- p. 5 Section (d), second paragraph on the page
tion is carried out in 2 × SSC, 40% formamide at 40°C. I have not tried this method, because this solvent removed DNA from the filters (see later section).
- p. 11 Table 2, last row
6 × SSC in 50% formamide
- p. 5 Section 2(d) Hybridization
carried out in 2 × SSC, 40% formamide at 40°C. I have not tried this method, because this solvent removed DNA from the filters (see later section)
Judge's note: Page 5 image confirms the sentence. Table 2 on page 11 has a single formamide row, 6 × SSC in 50% formamide, with 58% retained at 50°C and 50% at 65°C. The prose of section (f) does not discuss formamide. The forward pointer therefore supports the statement only loosely (formamide solvents in general), not the specific solvent named. This is a wording imprecision.
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Wording Text: "Increasing the salt concentration does improve the retention of the DNA at any given temperature (Table 2)", but in the 65°C column of Table 2 retention is 77, 97, 95, 97 for 2×, 6×, 10×, 20× SSC, so it is not monotonic (6× SSC 97 > 10× SSC 95; 20× equals 6×).
- p. 11 Section (f), text above Table 2
Increasing the salt concentration does improve the retention of the DNA at any given temperature (Table 2)
- p. 11 Table 2, 65°C column
97
- p. 11 Table 2
10 × SSC 95 83 73
- p. 11 Table 2, 65°C column
6× SSC 97 ... 10× SSC 95
Judge's note: Table 2 read from the page 11 image. 65°C column: 77, 97, 95, 97. 80°C: 62, 76, 83, 88. 90°C: 48, 56, 73, 81. The trend holds at 80 and 90°C. At 65°C there is a 2-point dip from 6× to 10× SSC and no gain from 6× to 20×. With about 650 c.p.m. per filter this is plausibly within experimental error, so the issue is over-general wording; a misprinted table value cannot be established. The text's own example (2× SSC at 65°C, 77, about equal to 6× SSC at 80°C, 76) agrees with the table as printed.
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Typo Misspelling: "like all other photosensitivie materials" should read "photosensitive".
- p. 13 Section (g), paragraph beginning 'For ionizing radiation'
like all other photosensitivie materials
Judge's note: Page 13 image prints "photosensitivie" with the extra "i"; it is in the print, not only in the text layer.
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Typo Misspelling in the Conclusion: "after the DNA frqgments have been separated" should read "fragments".
- p. 17 Section 3 Conclusion, line 2
after the DNA frqgments have been separated
Judge's note: Page 17 image, Conclusion line 2, prints "frqgments" with a "q" in place of "a". The word "fragments" is printed correctly elsewhere in the same paragraph, so this is a printed typo and not an OCR artefact.
Second check: none (judge only)