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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 44 (1997), S. 321 -326 
    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
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  • 2
    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
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  • 3
    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
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  • 4
    ISSN: 0749-503X
    Keywords: yeast ; genome project ; chromosome IV ; GDH ; SHR3 ; UGA4 ; NHP2 ; HEM3 ; MGT1 ; SHM1 ; ASF2 ; Gly-tRNA ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The complete nucleotide sequence of a 39 090 bp segment from the left arm of yeast chromosome IV was determined. Twenty-one open reading frames (ORFs) longer than 100 amino acids and a Gly-tRNA gene were discovered. Nine of the 21 ORFs (D0892, D1022, D1037, D1045, D1057, D1204, D1209, D1214, D1219) correspond to the previously sequenced Saccharomyces cerevisiae genes for the NAD-dependent glutamate dehydrogenase (GDH), the secretory component (SHR3), the GABA transport protein (UGA4), the high mobility group-like protein (NHP2), the hydroxymethylbilane synthase (HEM3), the methylated DNA protein-cysteine S-methyltransferase (MGT1), a putative sugar transport protein, the Shm1 protein (SHM1) and the anti-silencing protein (ASF2). The inferred amino acid sequences of 11 ORFs show significant similarity with known proteins from various organisms, whereas the remaining ORF does not share any similarity with known proteins. The nucleotide sequence has been entered in the EMBL data Library under the Accession Number X99000.©1997 John Wiley & Sons, Ltd.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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