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Biomedical subjects

D M Steffensen

Publications and source records attributed to D M Steffensen.

At least 19 recordsLinked to original sources
PubMed1987

Localization of zein genes in maize.

The band patterns of zein polypeptides were determined for many commercial inbred corn lines and maize stocks using isofocusing in agarose gels and sodium dodecyl sulfate (SDS)-urea gels. Each inbred line or homozygous maize strain genotype has a distinct zein profile which has been catalogued according to the distance of charge migration and molecular weight (kilodaltons). Several zein polypeptides were mapped to chromosomes 4 and 10 with the use of reciprocal translocations. The mapping of at least two polypeptides on distal 4L and 10L had not been previously reported. The general methods used in the present research will permit the mapping of all the zein polypeptides to chromosomal sites.

Chromosome Mapping↗
PubMed1984

Chromosomal sites of integration of simian virus 40 DNA sequences mapped by in situ hybridization in two transformed hybrid cell lines.

Simian virus 40 DNA sequences, integrated on human chromosome 7 in two transformed human-mouse hybrid somatic cell lines, were mapped to a specific chromosomal locus by in situ hybridization. To detect the integrated viral DNA by in situ hybridization, we increased the sensitivity of the technique by using as a probe 125I-labeled simian virus 40 cRNA (2 X 10(9) to 3 X 10(9) dpm/micrograms) prepared by in vitro transcription of simian virus 40 DNA with high-specific-radioactivity [125I]CTP. Although the viral nucleic acid was shown by blot hybridization in the two cell lines to be integrated in different restriction fragments, it was shown by in situ hybridization in the two cell lines to map to the same position, q31, on the long arm of human chromosome 7. The viral DNA integration sites were localized with a precision of +/- 1 silver grain diameter, equivalent to about 6.2 X 10(7) nucleotide pairs in the human genome. The procedures we describe may be adapted for localization of any gene on diploid chromosomes that can be cloned in a recombinant DNA vector.

Animals↗
PubMed1981

The distribution of two highly repeated DNA sequences within Drosophila melanogaster chromosomes.

In situ hybridization using 3H-RNA probes has been used to localize the sequences found in two satellites of density 1.705 g/cc and 1.672 g/cc to specific sites within the chromosomal complement. A detailed analysis of the sites on the S chromosome was carried out using the acute series of inversions to relate the heterochromatic breakpoint relative to the location of the sequence on this chromosome. It has also been possible to establish the order of arrangement of 1.705 and 1.672 DNA at the heterochromatic-euchromatic junction on chromosome 3(R). A mitotic map is provided. The Tm of hybrids formed in situ showed that the hybrids were representative of the sequences being analyzed. The two satellites also were traced through a number of purification procedures to show that a covalent linkage may be likely between the 1.705 g/cc and 1.672 g/cc satellite as predicted from in situ hybridization analyses.

Animals↗
PubMed1980

Quantitation of in situ hybridization of ribosomal ribonucleic acids to human diploid cells.

The hybridization of 5S and 28S ribosomal RNAs to human fibroblast and leukocyte cells was used as a model system to quantitative the technique of in situ hybridization for human diploid cell types. Quantitation consisted of counting (scoring) the number of grains formed over both interphase nuclei and metaphase chromosomes on slides after various hybridization procedures. The average number of grains/nucleus per slide was then used to determine hybridization percentages. As with nitrocellulose filter hybridizations the kinetics of in situ hybridizations can be fit with a single first-order rate-constant. However, the in situ hybridization rate was approximately 10 times slower than the corresponding filter hybridization rate. The efficiency of in situ hybridization was found to range between 5 and 15% for both leukocyte and fibroblast cell types and for both metaphase and interphase nuclei. Determination of the parameters of the in situ hybridization reaction of ribosomal RNAs to diploid chromosomes define the experimental conditions needed for the localization of single copy genes to diploid chromosomes.

Cells, Cultured↗
PubMed1977

Partial trisomy of the long arm of human chromosome 1 as demostrated by in situ hybridization with 5S ribosomal RNA.

In a newborn boy with multiple malformations, a tandem duplication was detected at the distal end of the long arm of one human chromosome 1. The Giemsa bands, 1q31 to 1q43--44, were repeated serially. Since 5S rRNA genes are located at 1q42--43, in situ hybridization of 125I 5S rRNA with fixed chromosome preparations was used to confirm the chromosomal duplication. The infant exhibited numerous developmental and clinical abnormalities as might be expected with an abnormality of chromosome structure relating to a ribosome component.

Chromosomes, Human, 1-3↗
PubMed1973

The use of iodinated RNA for gene localization.

Carrier-free iodination of 5S RNA with (125)I yields a probe suitable for use in cytological RNA-DNA hybridization studies. The genes coding for 5S ribosomal RNA in Drosophila could be localized by autoradiography after a 2-day exposure, whereas a 2-month exposure is needed when the best available [(3)H]RNA is used. The procedure introduces one covalently bound (125)I atom per 100 nucleotides, resulting in a specific activity of over 10(8) dpm/mug of RNA. The method may be readily applied to other problems involving molecular hybridization techniques.

Animals↗