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C W Schmid

Publications and source records attributed to C W Schmid.

At least 73 records · Page 4Linked to original sources
PubMed1983

Species-specific homogeneity of the primate Alu family of repeated DNA sequences.

We have determined the base sequence of several cloned Alu family members from the DNAs of a new world monkey (owl monkey) and a prosimian (galago). The three owl monkey Alu family members reported here belong to a single 300 base pair consensus sequence which closely resembles the human Alu family consensus. The galago Alu family members can best be represented as belonging to either of two related but distinct consensus sequences. One of the two galago Alu family subgroups (Type I) more accurately resembles the human consensus sequence than does the other subgroup (Type II). In this work we compare base sequences of human and galago Type I Alu family members. There are several examples of species-specific differences between the human and Type I galago sequences indicating that the Alu family members are effectively homogenized within a species.

Animals↗
PubMed1982

The Alu family of dispersed repetitive sequences.

A family of related sequences that includes approximately 500,000 members is the most prominent short dispersed repeat family in primate and rodent DNA's. The primate sequence is approximately 300 base pairs in length and is composed of two imperfectly repeated monomer units, whereas the rodent repeat consists of only a single monomer. Properties of this repeat sequence, its flanking sequences in chromosomal DNA, and RNA's transcribed from it suggest that it may be a mobile DNA element inserted at hundreds of thousands of different chromosomal locations.

Animals↗
PubMed1981

A complex repeated DNA sequence within the Drosophila transposable element copia.

A 320 nucleotide repeated DNA sequence within the copia coding element of Drosophila melanogaster has been identified and characterized. This sequence has been localized by DNA-DNA hybridization and electron microscopic analysis of heteroduplexes to the approximate middle of the 5 kb copia coding region. The primary sequence of this repeated DNA has been determined. The sequence is composed of three related subunits, 35-37 nucleotides in length (A, B and C). This 105 nucleotide higher order repeat has apparently been duplicated twice to yield a complex repeated sequence, ABCA'B'C'A"B"C", which exhibits divergence among the individual subunits. This sequence is AT rich, as are the direct terminal repeats which flank the copia coding region, but does not contain any apparent homology with the terminal repeats. This repeated sequence contains three presumptive polyadenylation signals and two 25 nucleotide, imperfectly matched, inverted repeat sequences adjacent to two of the polyadenylation sequences.

Animals↗
PubMed1981

Renaturation rate studies of a single family of interspersed repeated sequences in human deoxyribonucleic acid.

We have investigated the renaturation kinetics of a single family of cloned interspersed repeated sequences isolated from human DNA. Cross-renaturation studies of individual cloned sequences reveal heterogeneity in both the renaturation rate and the thermal stability of heteroduplexes formed from members of this family of sequences. However, cloned members of this family all renature with approximately the same number of copies in the human genome, demonstrating that they are a single family of sequences by the criterion of DNA renaturation kinetics. When a single cloned member of the family is renatured with total human DNA as a function of temperature, the thermal stability of the renatured heteroduplexes is found to be independent of the renaturation temperature over the range 25 degrees C below to 4 degrees C above the melting temperature. Further, the number of genomic copies with which this cloned family member reacts is also independent of the renaturation temperature from 25 degrees C below up to the melting temperatures. These observations demonstrate a remarkable degree of homogeneity in the evolutionary sequence divergence of members of this family. These results also demonstrate that renaturation kinetics can accurately measure the number of genomic copies of interspersed repeated DNA sequences.

Base Sequence↗
PubMed1981

The evolution of a family of short interspersed repeats in primate DNA.

Human DNA contains 300 nucleotide interspersed repeated sequences which mostly belong to a single family of sequences called the Alu family. This work examines the evolution of this family of sequences in primates. Bonnet monkey (Macaque radiata) DNA contains a predominant family of 300 nucleotide repeats which has nearly the same restriction map as the human Alu family and which hybridizes to human Alu family repeats under Southern blotting conditions. Prosimian (Galago crassicaudatus pangeniesis) DNA also contains a prominent group of 300 nucleotide long repeated sequences which does not have the same restriction sites as the human Alu family but which does hybridize to the human Alu family under reduced stringency conditions.

Animals↗
PubMed1980

Pyrimidine-specific chemical reactions useful for DNA sequencing.

Potassium permanganate reacts selectively with thymidine residues in DNA (1) while hydroxylamine hydrochloride at pH 6 specifically attacks cytosine (2). We have adopted these reactions for use with the chemical sequencing method developed by Maxam and Gilbert (3).

Base Sequence↗
PubMed1980

Related single copy sequences in the human genome.

Human single copy DNA renatured under relatively non-stringent conditions (50 degrees C, 0.36 M Na+) forms two components with different thermal stabilities: a high temperature component melting at a temperature (81 degrees C, 0.18 M Na+) expected for well-paired duplex and a low temperature component melting at 55 degrees C (0.18 M Na+). The production of the high and low temperature components has been examined as a function of C0t (product of concentration and time in units of mol/s per l) value and renaturation temperature. The duplex formed has been characterized by its resistance to S1 endonuclease and its length has been determined by gel electrophoresis. As a result of these experiments and related controls we conclude that the low temperature component is not an artifact of DNA fragment length, nonspecific base pairing or hydroxyapatite chromatography conditions. We attribute the low thermal stability of this component to the renaturation of distantly related single copy sequences to form a highly mismatched duplex DNAs with an average length of about 100 base pairs.

Base Sequence↗
PubMed1980

Ubiquitous, interspersed repeated sequences in mammalian genomes.

DNA base sequence comparisons demonstrate that the principal family of 300-nucleotide interspersed human DNA sequences, the repetitive double-strand regions of HeLa cell heterogeneous nuclear RNA, and specific RNA polymerase III in vitro transcripts of cloned human DNA sequences are all representatives of a closely related family of sequences. A segment of approximately 30 residues of these sequences is highly conserved in mammalian evolution because it is also present in the interspersed repeated DNA sequences of Chinese hamsters. Further DNA sequence comparisons demonstrate that a portion of this highly conserved segment of repetitive mamalian DNA sequence is similar to a sequence found within a low molecular weight RNA that hydrogen-bonds to poly(A)-terminated RNA molecules of Chinese hamsters and a sequence that forms half of a perfect inverted repeat near the origin of DNA replication in papovaviruses.

Animals↗
PubMed1978

A critical examination of possible fractionations of human DNA according to base composition.

Human DNA has been fractionated according to base composition by sedimentation equilibrium in an HgCl2/Cs2SO4 density gradient, followed by sedimentation equilibrium in an actinomycin/cesium formate density gradient. The fractions of different base composition resulting from this procedure were subsequently analyzed by sedimentation equilibrium in CsCl, DNA renaturation kinetics, and electron microscopy. All fractions contain similar kinetic classes of repeated DNA sequences as judged by renaturation studies. Short (300 nucleotides) interspersed repeated sequences are found in all fractions with no noticeable enrichment for these sequences in any fraction. Repeated sequences from fractions of different base composition are partially able to cross-hybridize, demonstrating that nearly identical repeated sequences occur in molecules of different base composition. These findings are critically compared to reports of successful density gradient fractionations of different human DNA sequence classes.

Centrifugation, Density Gradient↗
PubMed1978

Fractionation of renatured repetitive human DNA according to thermal stability, sequence length, and renaturation rate.

Renatured repetitive human DNA sequences have been fractionated according to three criteria: length, thermal stability, and rate of renaturation. Satellite sequences are found in the long repetitive sequence fractions and renatured satellite sequences are well base paired by the criterion of thermal stability. No satellites are observed in short repeated sequences. Short repeated sequences are interspersed with single copy sequences and are poorly base paired. This implies satellite components are relatively homogeneous in base sequence whereas short interspersed repeated sequences are inexact copies of each other. A method for isolating satellite DNAs based on their high thermal stabilities is discussed.

Base Sequence↗