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Digitale Medien

Chromatin self-organization by mutation bias (1994)

Holmquist, Gerald P.

Springer

Journal of molecular evolution 39 (1994), S. 436-438

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ISSN: 1432-1432

Schlagwort(e): Sequence evolution ; Mutation pressure ; Nucleosomes

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Proteins, on binding to a DNA sequence, alter the frequency and quality of mutations that occur in the sequence. This represents a reverse flow of information from proteins to DNA. Nucleosome binding causes patterns of UV-induced damage which, when converted to mutations by replication, will phase nucleosomes. We propose that DNA binding proteins create their own high- or low-affinity binding sites along DNA sequences by biased mutational pressure.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00173411

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Digitale Medien

DNA replication asynchrony between the paternal and maternal alleles of imprinted genes does not straddle the R/G transition (1997)

Drouin, Régen ; Boutouil, Mohamed ; Fetni, Raouf ; [weitere]

Springer

Chromosoma 106 (1997), S. 405-411

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ISSN: 1432-0886

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Abstract. Imprinted autosomal loci apparently reside in very large chromosomal domains that exhibit asynchrony in replication of homologous alleles during the DNA synthesis phase. Replication asynchrony can be cytogenetically visualized by a replication-banding discordance between homologous bands of a given pair of chromosomal homologs. The replication time of a chromosomal band at high resolution can be determined by blocking DNA synthesis at the R/G-band transition and using replication banding. The R/G transition reflects the transition from early (R-) to late (G- and C-) band DNA replication. We studied discordance between two groups of homologous chromosomal bands: (a) four bands, 6q26–27, 11p13, 11p15.5 and 15q11.2–12, each containing at least one imprinted gene; and (b) nine bands containing no known imprinted genes. Fifty pairs of chromosomes were analyzed at high resolution after R/G transition blocking and late 5-bromo-2′-deoxyuridine incorporation. The rate of discordance was the same for bands containing imprinted genes and for control bands. Both homologous bands of a pair replicate either before or after the R/G transition and do not straddle the R/G transition. Repression associated with imprinting does not appear to involve late replication at the band level of resolution. Tissue-specific inactivation is associated with DNA methylation and late replication, whereas allele-specific inactivation is associated with DNA methylation but not with delayed or late replication.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s004120050262

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Digitale Medien

Sister chromatid exchange and chromosome organization based on a bromodeoxyuridine Giemsa-C-banding technique (TC-Banding) (1975)

Holmquist, Gerald P. ; Comings, David E.

Springer

Chromosoma 52 (1975), S. 245-259

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ISSN: 1432-0886

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Abstract Hoechst 33258 fluorescent staining of bromodeoxyuridine substituted chromosomes provided a high resolution technique for following the segregation of replicated chromosomal DNA (Latt, 1973). Modifications have produced the same results after Giemsa staining (Wolff and Perry, 1975). Since this does not necessarily require Hoechst (Korenberg and Freedlander, 1975), we call this bromodeoxyuridine-Giemsa banding (BG-banding). We here describe a further modification which allows one to follow the T-rich strand of the AT-rich satellite DNA of C-band heterochromatin. We call this TC-banding. This technique was used to examine metacentric marker chromosomes found in mouse L-cells that contain many interstitial blocks of centromeric-type heterochromatin in each arm plus the usual two blocks of centromeric heterochromatin. One of the advantages of this technique for such chromosomes is that it is possible to distinguish first from second cell cycle sister chromatid exchange and unambiguously detect centromeric sister chromatid exchange. We found some chromosomes to have high rates of centromeric sister chromatid exchange. After one cycle in bromodeoxyuridine we could examine the satellite polarity of the heterochromatic DNA. Since there was no change in satellite polarity in any of the heterochromatic blocks, marker chromosomes could not have been formed by paracentric inversions, inverted insertions or inverted translocations. These results allow the formulation of several rules of chromosome organization.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00332114

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Digitale Medien

Quantitative measurements of fluorescently-stained DNA in gels from photographic images (1985)

Willis, Charles E. ; Holmquist, Gerald P.

Weinheim : Wiley-Blackwell

Electrophoresis 6 (1985), S. 259-267

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ISSN: 0173-0835

Schlagwort(e): Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: Photography under ultraviolet illumination is used routinely to record the results of gel electrophoresis of DNA when a fluorescent dye, which binds to DNA, is present in the gel. The distribution of DNA in the gel can be determined accurately from the photographic negative when the absorbance is interpreted according to the nonlinear film darking function, when the contrast of the film is calculated, and when the images are corrected for uneven ultraviolet transillumination. The contrast can be calculated from the images of a fluorescent plastic intensity standard. The local intensity of the unbound-dye fluorescence can be used to correct images for uneven illumination. Using this approach, relative abundances of DNA fragments, compared within each electrophoretic track, were measured within an average error of 6.6% of the expected value with no evidence of systematic error. Quantitative comparisons were valid anywhere on the film for a 50:1 range of intensities, with errors distributed normally with a standard deviation of ± 10 % of the expected value.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/elps.1150060603

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