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  • 1
    Electronic Resource
    Electronic Resource
    Molecular Evolution of the Globin Gene Cluster E in Two Distantly Related Midges, Chironomus pallidivittatus and C. thummi thummi (1998)
    Springer
    Journal of molecular evolution 46 (1998), S. 589-601 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Globin — Hemoglobin — Molecular evolution — Multigene family — Gene conversion — Chironomus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. We have studied the evolutionary dynamics of a cluster of insect globin genes by comparing the organization and sequence of the gene group in two distantly related species, Chironomus pallidivittatus and C. t. thummi. Although the general architecture of the globin gene cluster has been conserved, we have found an additional, previously undescribed gene (named Cpa F) in C. pallidivittatus which shows signs of accelerated sequence evolution at nonsynonymous codon positions. This new gene is clearly functional, as demonstrated by Northern analysis. Comparison of paralogous and orthologous genes reveals patterns of intraspecific sequence homogenization. The head-to-head-oriented globin 3 and 4 gene pairs in C. t. thummi and the gb 4 gene pair in C. pallidivittatus have been efficiently homogenized, probably by gene conversion, in their promoter and coding regions. Inverted transcriptional orientation seems to favor efficient conversion. The orthologous genes from C. t. thummi and C. pallidivittatus reveal different levels of sequence conservation, ranging from 85.3 to 94.7% amino acid identity. Surprisingly, globin gene E, for which up to now no corresponding protein has been detected in the larval hemolymph of C. t. thummi, shows the highest degree of interspecies sequence conservation. This points to an essential, as yet unknown function of this globin. The usefulness of globin gene comparisons for dating speciation events in Chironomus is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006339
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  • 2
    Electronic Resource
    Electronic Resource
    Sequence and evolution of the gene for the monomeric globin I and its linkage to genes coding for dimeric globins in the insect Chironomus thummi (1995)
    Springer
    Journal of molecular evolution 40 (1995), S. 354-361 
    Details
    ISSN: 1432-1432
    Keywords: Insect globin genes ; Molecular evolution ; Alleles ; In situ hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We isolated genomic clones containing sequences encoding globins I and IA from a Chironomus thummi thummi genomic library. Three clones contain globin IA (ctt-1A) genes, while one contains a globin I (ctt-1) gene. The coding regions of the four genes are identical except for the single base substitution accounting for the globin I/IA polymorphism. The noncoding DNA flanking the coding region is more than 98% similar, confirming a previous hypothesis that the globin ctt-1 and ctt-1A genes are alleles. Hemoglobins I and IA are monomeric in the insect hemolymph. Earlier in situ hybridization studies suggested that monomeric and dimeric globin genes are clustered at different chromosomal loci. In situ hybridization of ctt-1 DNA to polytene salivary gland chromosomes places the ctt-1 gene on the same band as genes for the dimeric globins IIβ and VIIB, forcing revision of the earlier hypothesis that genes for monomeric and dimeric globin genes are at different loci. The evolution of the ctt-1 and ctt-1A alleles and of the two globin gene loci are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164021
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  • 3
    Electronic Resource
    Electronic Resource
    Complex Evolution of Tandem-Repetitive DNA in the Chironomus thummi Species Group (1997)
    Springer
    Journal of molecular evolution 44 (1997), S. 321 -326 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Chironomus — Satellite DNA — Tandem-repetitive DNA — Molecular Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The subspecies Chironomus thummi thummi and C. t. piger display dramatic differences in the copy number and chromosomal localization of a tandemly repeated DNA family (Cla elements). In order to analyze the evolutionary dynamics of this repeat family, we studied the organization of Cla elements in the related outgroup species C. luridus. We find three different patterns of Cla element organization in C. luridus, showing that Cla elements may be either strictly tandem-repetitive or be an integral part of two higher-order tandem repeats (i.e., Hinf[lur] elements, Sal[lur] elements). All three types of Cla-related repeats are localized in the centromeres of C. luridus chromosomes. This suggests that the dispersed chromosomal localization of Cla elements in C. t. thummi may be the result of an amplification and transposition during evolution of this subspecies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006149
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  • 4
    Electronic Resource
    Electronic Resource
    Chromatophore development and cell interactions in the skin of xiphophorine fish (1978)
    Springer
    Development genes and evolution 184 (1978), S. 115-134 
    Details
    ISSN: 1432-041X
    Keywords: Cell interactions ; Fish chromatophores ; Xiphophorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Die Entwicklung von Chromatophoren in regenerierender Haut von Fischen der GattungXiphophorus wurde als Modell zur Untersuchung von Zellinteraktionen benutzt. Der Ablauf der Chromatophorenentwicklung nach Induktion durch Entfernen der Haut wird beschrieben unter besonderer Berücksichtigung der Melanophorendifferenzierung. Zwischen Makro- und Mikromelanophoren, die in der Haut der Xiphophorini vorkommen, existieren folgende Wechselwirkungen: 1. die Makromelanophoren inhibieren die Differenzierung von Melanocyten und Mikromelanophoren 2. die Makromelanophoren induzieren den Abbau von vollentwickelten Mikromelanophoren in ihrer Nachbarschaft. Diese Makro-Mikromelanophoren-Wechselwirkungen, sind außerordentlich zelltyp-spezifisch. Sie sind unabhängig vom Fischgenotyp in der Haut verschiedener Fischarten der GattungXiphophorus wirksam. Sie sind auch dann nachweisbar, wenn Makromelanophoren der einen Fischart in die Haut einer anderen Fischart implantiert werden. Die Rolle der Zellinteraktionen für die Pigmentmusterbildung wird diskutiert.
    Notes: Summary Regeneration-induced development of chromatophores in the skin of fish was used to study cell interactions affecting cell differentiation and cell destruction. The typical differentiation process of chromatophores in the regenerating fish skin is described with special interest in the differentiation of macro- and micromelanophores. Between micro- and macromelanophores two types of cell interactions were found: 1. The macromelanophores inhibit the differentiation of melanocytes and micromelanophores 2. the macromelanophores induce the destruction of micromelanophores in their vicinity. These cell interactions are very specific to cell type, that means they are strictly limited to macro- and micromelanophores. On the other hand, the effectiveness of these cell interactions isnot limited to one genotype or one species of Xiphophorine fish. The inhibiting and the destruction-inducing influence of macromelanophores upon micromelanophores is shown for three different species of Xiphophorine fish. The role of cell interaction in chromatophore development is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848221
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  • 5
    Electronic Resource
    Electronic Resource
    The organization, localization and nucleotide sequence of the histone genes of the midge Chironomus thummi (1991)
    Springer
    Chromosoma 101 (1991), S. 25-31 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Several histone gene repeating units containing the genes for histones H1, H2A, H2B, H3 and H4 were isolated by screening a genomic DNA library from the midge Chironomus thummi ssp. thummi. The nucleotide sequence of one complete histone gene repeating unit was determined. This repeating unit contains one copy of each of the five histone genes in the order and orientation 〈H3 H4〉 〈H2A H2B〉 H1〉. The overall length is 6262 bp. The orientation, nucleotide sequence and inferred amino acid sequence as well as the chromosomal arrangement and localization are different from those reported for Drosophila melanogaster. The codon usage also shows marked differences between Chironomus and Drosophila. Thus the histone gene structure reported for Drosophila is not typical of all insects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00360683
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  • 6
    Electronic Resource
    Electronic Resource
    Cloning and analysis of ribosomal DNA of Chironomus thummi piger and chironomus thummi thummi (1982)
    Springer
    Chromosoma 87 (1982), S. 389-407 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The ribosomal DNAs from Ch. thummi piger and Ch. th. thummi were cloned and analysed by a variety of restriction endonucleases. Comparison of rDNA clones from the two subspecies revealed a considerable length difference: the length of the analysed rDNA cistrons is approximately 9.0 kb for Ch. th. piger and approximately 14.5 kb for Ch. th. thummi. The nearly 5 kb additional DNA in Ch. th. thummi is clearly located within the non-transcribed spacer region, and consists of AT-rich, reptitive DNA elements. These elements with a basic repeat length of approximately 120 bp, are arranged tandemly in stretches of up to about 50 identical copies, which are characterized by a cleavage site for ClaI restriction endonuclease. They are found only in the Ch. th. thummi rDNA clones and not in the Ch. th. piger clones. Southern hybridizations between cloned ribosomal DNA and “centromeric” highly repetitive DNA have shown that the ribosomal repetitive Cla-elements are closely related to a highly repetitive DNA sequence family, which is present in various chromosomal sites particularly the centromeres. Sequence analysis has revealed more than 90% homology between the ribosomal Cla-elements and the “centromeric” Cla-elements. — Since it is clear from cytological investigations that Ch. th. piger with the small rDNA repeating unit is the phylogenetically older subspecies, we postulate a transposition of Cla-elements into the nucleolar DNA during the evolution of Ch. th. thummi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327181
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  • 7
    Electronic Resource
    Electronic Resource
    The sex determining region of Chironomus thummi is associated with highly repetitive DNA and transposable elements (1993)
    Springer
    Chromosoma 102 (1993), S. 553-562 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The dominant male sex determiner in chromosome III of the midge Chironomus thummi thummi is closely linked to a large cluster of tandem-repetitive DNA elements, the Cla elements, which are otherwise highly repetitive and distributed over more than 200 sites on all chromosomes. Chromosome III displays a hemizygous cluster of Cla elements in males but not in females. The chromosomal location of this hemizygous Cla element cluster is in the region of the male determiner M as localized by cytogenetic analysis. With Cla elements as hybridization probe, it was possible to clone a large part of the sex determining region. Molecular analysis of the DNA of males and females in this region displayed a number of differences between the two sexes. One striking difference is an unusual transposable element associated with the male sex determining region. The sex determining region also contains several other tandem-repetitive DNA elements in addition to the Cla elements. They are interspersed with single copy DNA. The accumulation of repetitive elements in the sex determining region is interpreted as the result of a lack of recombination between the male/female heteromorphic region, although recombination in the other sections of chromosome III occurs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00368348
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  • 8
    Electronic Resource
    Electronic Resource
    Different repetition frequencies of a 120 base-pair DNA-element and its arrangement in Chironomus thummi thummi and Chironomus thummi piger (1981)
    Springer
    Chromosoma 84 (1981), S. 61-66 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The repetition frequency of a highly repetitive DNA sequence has been measured in the genomes of Ch. thummi thummi and Ch. th. piger. This sequence is known to be involved in the evolutionary duplication of defined chromosomal segments leading to a significant increase in the genome size of Ch. th. thummi. Reassociation of this highly repetitive DNA sequence which has a repeat length of 120 base-pairs, with total Ch. th. thummi and Ch. th. piger DNA has shown that the repetition frequency in the Ch. th. thummi DNA is 5.5 fold higher than in Ch. th. piger. In both genomes a 120 base-pair sequence is present as tandemly repeated sequence as shown by Southern analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293363
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  • 9
    Electronic Resource
    Electronic Resource
    Two AT-rich satellite DNAs in the chironomid Glyptotendipes barbipes (Staeger) (1980)
    Springer
    Chromosoma 79 (1980), S. 315-328 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Two AT-rich satellite DNAs are present in the genome of Glyptotendipes barbipes. The two satellites have densities of 1.680 g/cm3 (=21% GC) and of 1.673 g/cm3 (=13% GC) in neutral CsCl-density gradients. The main band DNA has a density of 1.691 g/cm3 (=32% GC). This value is in agreement with the 33% GC-content of G. barbipes DNA calculated from thermal denaturation (TM=83° C). — In brain DNA as well as in salivary gland DNA the two satellite sequences together comprise 12–15% of the total G. barbipes DNA. Comparisons of the density profiles of DNA extracted from polytene and non-polytene larval tissue gave no hints for underreplication of the satellite DNAs during polytenization. — The two satellite DNAs have been isolated from total DNA by Hoechst 33258-CsCl density centrifugation and then localized in the polytene salivary gland chromosomes by in situ hybridization. Both satellite sequences hybridize to all heterochromatic centromere bands of all four chromosomes of G. barbipes. Satellite I (1.673 g/cm3) hybridizes mainly with the middle of the heterochromatin, satellite II (1.680 g/cm3) hybridizes with two bands at the margin of the heterochromatin. In situ hybridization with polytene chromosomes of Chironomus thummi revealed the presence of G. barbipes satellite sequences also in the Ch. thummi genome at various locations, mainly the centromere regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327322
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  • 10
    Electronic Resource
    Electronic Resource
    Gasanalyse (1927)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 71 (1927), S. 55-66 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01388949
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