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J B Dodgson

Publications and source records attributed to J B Dodgson.

12 recordsLinked to original sources
PubMed1991

Adult chicken alpha-globin gene expression in transfected QT6 quail cells: evidence for a negative regulatory element in the alpha D gene region.

The chicken adult alpha-globin genes, alpha A and alpha D, are closely linked in chromosomal DNA and are coordinately expressed in vivo in an approximate 3:1 ratio, respectively. When subcloned DNAs containing one or the other gene are stably transfected into QT6 quail fibroblasts, the alpha A-globin gene is expressed at measurable RNA levels, but the alpha D gene is not. The alpha A gene expression can be considerably increased by the presence of a linked Rous sarcoma virus long terminal repeat enhancer, but that of the alpha D gene remains undetectable. Transfection with subclones containing both genes, either in cis or in trans, leads to considerably reduced alpha A RNA levels and still no observable alpha D gene expression. Transfection with deleted subclones suggests that maximal expression levels in this system require the alpha A-globin gene promoter, as opposed to that of the alpha D gene, but that such expression is greatly reduced by one or more DNA sequences which lie approximately 2,000 base pairs upstream of the alpha A gene, within the body of the alpha D gene.

Animals↗
PubMed1985

Replacement variant histone genes contain intervening sequences.

The nucleotide sequences of two chicken histone genes encoding replacement variant H3.3 polypeptides are described. Unlike the replication variant genes of chickens (and almost all other organisms), these genes contain intervening sequences; introns are present in both genes in the 5' noncoding and coding sequences. Furthermore, the replacement variant histone mRNAs are post-transcriptionally polyadenylated. The locations, but not the sizes, of the two introns within the coding segments of the two genes have been exactly conserved, whereas the intron positions in their respective 5' flanking regions differ. Although both H3.3 genes predict the identical histone polypeptide sequence, they are as different from one another as each of them is from a more common replication variant H3.2 gene in silent base substitutions within the coding sequences. Thus, the H3.3 polypeptide sequence has been precisely maintained over a great evolutionary period, suggesting that this class of histones performs a strongly selected biological function. Although replacement variant histones can account for more than 50% of the total H3 protein in the nuclei of specific chicken tissues, the steady-state level of H3.3 mRNA is nearly the same (and is quite low) in all tissues and ages of animals examined. These properties suggest novel mechanisms for the control of the basal histone biosynthesis which takes place outside of the S phase of the cell cycle.

Age Factors↗
PubMed1979

Isolation of the chicken beta-globin gene and a linked embryonic beta-like globin gene from a chicken DNA recombinant library.

A library of random chicken DNA fragments, 15-22 kb long, has been prepared in the vector lambda Charon 4A. This library was screened with combined adult and embryonic globin cDNA, and several independent globin gene-containing recombinants were isolated. One of these recombinants, lambda Chicken beta-globin 1 (lambda C beta G1), contains the adult chicken beta-globin gene and a closely linked embryonic beta-like globin gene. Both genes are transcribed in the same direction with the adult gene located 5' to the embryonic gene. Electron microscopic visualization of R loop structures generated by hybridization of globin RNA to lambda C beta G1 demonstrates that both globin genes contain major intervening sequences about 800 bp long, similar to those present in mammalian beta-globin genes. The adult beta-globin gene also contains a minor (approximately 100 bp long) intervening sequence analogous to the one observed in mammalian beta-globin genes. Restriction enzyme analysis of the adult beta-globin gene on lambda C beta G1 is consistent with the hypothesis that its two intervening sequences occur in the same positions with respect to the beta-globin amino acid sequence as do the corresponding mammalian intervening sequences.

Animals↗
PubMed1979

Gene localization by chromosome fractionation: globin genes are on at least two chromosomes and three estrogen-inducible genes are on three chromosomes.

Chicken metaphase chromosomes were partially purified by rate zonal centrifugation, and DNA was prepared from each of the fractions of the sucrose gradient. The DNA was digested with various restriction enzymes and subjected to electrophoresis in agarose gels. The DNA was transferred to nitrocellulose filters (as described by Southern), and the filters were hybridized with cDNA probes. Four globin genes alpha A, alpha D, beta, and rho or epsilon are located on at least two chromosomes, and three of the estrogen-inducible genes of the hen oviduct--ovalbumin, ovomucoid, and transferrin--are on three different chromosomes. These experiments also confirm our earlier assignment of the endogenous viral sequence related to Rous-associated virus-0 to a separate (and larger) chromosome than the cellular sequence related to the transforming gene of avian sarcoma virus (cellular sarc), although it now appears that cellular sarc is on a small macrochromosome, rather than on a microchromosome.

Animals↗
PubMed1978

Analysis of the adult and embryonic chicken globin genes in chromosomal DNA.

Globin-specific mRNA has been purified from the red blood cells of anemic adult hens and from those of 5-day and 7-day chick embryos. These RNA preparations were used to synthesize labeled cDNA for solution and filter hybridization (Southern blotting) experiments. Hybridization of cDNAs prepared with separated adult alpha- and beta-mRNAs and of rabbit globin-specific probes to restriction enzyme-digested, filter-bound chicken chromosomal DNA has shown that the adult globin genes of the chicken exist within EcoRI-cleaved chromosomal DNA fragments which are 4.3, 6.0, and 12.5 kilobase pairs (kbp) in size. These fragments contain the majority or entirety of the adult alpha D, beta, and alpha A genes, respectively. Furthermore, we present evidence that the predominant chicken embryonic globins are contained within EcoRI fragments 9.4 and 15 kbp in size. Evidence is also presented that the same globin organization exists in several different breeds of chickens and in several chicken culture cell types. Finally, it is demonstrated that the pattern of globin-specific hybridization to reticulocyte chromosomal DNA digested with several restriction enzymes is unchanged during erythropoietic development.

Animals↗
PubMed1977

Synthesis and thermal melting behavior of oligomer-polymer complexes containing defined lengths of mismatched dA-dG and dG-dG nucleotides.

Model DNA polymers containing heteroduplex regions of defined sequence and size were synthesized using polynucleotide phosphorylase and calf thymus terminal transferase. Heteroduplexes were of the form (dG)n-d(C12AmC-x), where m - 1-6, and (dG)n-d(C10GmC-x), where m = 1 and 3-5. Thermal melting studies of the model DNAs indicated that the heteroduplex regions did not disrupt the cooperative interaction between the flanking regions of dG-dC base pairs. thus, it is possible that the heteroduplex nucleotides are accommodated in a stacked helical structure.

DNA Nucleotidyltransferases↗
PubMed1977

Action of single-strand specific nucleases on model DNA heteroduplexes of defined size and sequence.

The sensitivity of the model DNAs containing dA-dG and dtg-dG heteroduplex regions of defined length to S1 and mung bean single-strand specific nucleases was tested by polyacrylamide gel electrophoretic analysis of the distribution of product oligonucleotides. Single-base mismatch heteroduplexes were extremely resistant to these nucleases, although low levels of cleavage at the heteroduplex nucleotide were observed at high nuclease concentrations. The nuclease sensitivity of dA-dtg heteroduplex regions increased gradually as the length of the heteroduplex region increased frome one to six nucleotides. The sensitivity of dG-dG heteroduplexes three to five nucleotides long was considerably greater than that of the single dtg-dG mismatch.

DNA, Single-Stranded↗
PubMed1975

Transmission of stability (telestability) in deoxyribonucleic acid. Physical and enzymatic studies on the duplex block polymer d(C15A15) - d(T15G15).

The properties of the duplex block polymer d(C15A15) - d(T15G15) were examined by thermal denaturation and nuclease susceptibility studies in the absence and presence of drugs (actinomycin and netropsin) which bind specifically to only one end of the block polymer. The nucleotide composition of one region of this synthetic double-helical DNA affected the properties of a contiguous but remote region. Furthermore, the binding of actinomycin influenced the properties of both the binding and nonbinding regions. These findings suggest a mechanism for gene regulation at a distance.

Adenosine Monophosphate↗