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  • 1
    ISSN: 1432-1432
    Keywords: Key words: Short interspersed sequence elements (SINES) — Retroposition — Alu evolution — Alu RNA folding — Primate lineages — Prosimians — Genomic repeats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. To get insight into the early evolution of the primate Alu elements, we characterized sequences of these repeats from the Malagasy prosimians, lemurs (Lemuridae) and sifakas (Indriidae), as well as from galagos (Lorisidae). These sequences were compared with the oldest Alu species known from the human genome: dimeric Alu J and S and free Alu monomers. Our analysis indicates that about 60 Myr ago, before the prosimian divergence, free left and right monomers formed an Alu heterodimer connected by a 19-nucleotide-long A-rich linker. The resulting elements successfully propagated in diverging primate lineages until about ∼20 Myr ago, conserving similar sequence features and essentially the same Alu RNA secondary structure. We suggest that until that time the same ``retropositional niche'', molecular machinery making possible the proliferation by retroposition, constrained the evolution of Alu elements in extant primate species. These constraints became subsequently relaxed. In the Malagasy prosimians the dimeric Alu continued to amplify after acquiring a 34- to 36-nucleotide extension of their linker segment, whereas in the galago genome the ``retropositional niche'' was occupied by novel short elements.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1432
    Keywords: Key words: Human evolution — DNA polymorphisms — Dystrophin locus — Population size — Neutral evolution — Mutation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Neutral DNA polymorphisms from an 8-kb segment of the dystrophin gene, previously ascertained in a worldwide sample (n= 250 chromosomes), were used to characterize the population ancestral to the present-day human groups. The ancestral state of each polymorphic site was determined by comparing human variants with their orthologous sites in the great apes. The ``age before fixation'' of the underlying mutations was estimated from the frequencies of the new alleles and analyzed in the context of these polymorphisms' distribution among 13 populations from Africa, Europe, Asia, New Guinea, and the Americas (n= 860 chromosomes in total). Seventeen polymorphisms older tan 100,000–200,000 years, which contributed ∼90% to the overall nucleotide diversity, were common to all human groups. Polymorphisms endemic to human groups or continentally restricted were younger than 100,000–200,000 years. Africans (six populations) with 13 such sites stood out from the rest of the world (seven populations), where only 2 population-specific variants were observed. The similarity of the frequencies of the old polymorphisms in Africans and non-Africans suggested a similar profile of genetic variability in the population before the modern human's divergence. This ancestral population was characterized by an effective size of about 10,000 as estimated from the nucleotide diversity; this size may describe the number of breeding individuals over a long time during the Middle Pleistocene or reflect a speciation bottleneck from an initially larger population at the end of this period.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1432
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 42 (1996), S. 66-72 
    ISSN: 1432-1432
    Keywords: SINEs ; B1 subfamilies ; 7SL RNA-derived retroposons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have determined sequences of PCR-amplified B 1 elements from hamster and rat (Myomorpha), chipmunk (Sciuromorpha), and guinea pig (Caviomorpha). Between three and six B 1 subfamilies were found in these species. In the phylogenetic analysis Bl sequences of hamster, mouse, and rat clustered separately from those of chipmunk and those of guinea pig. This is consistent with an independent evolution of B1 elements in separate rodent lineages. We exclude the possibility of convergent mutations to explain certain diagnostic characters within the modern B1 quasi-dimers and view these elements as mosaic structures assembling preexisting mutations. Furthermore, the presence of Alu-like structural motifs supports the hypothesis of the monophyletic origin of Alu and B1 repeats, i.e., from a common 7SL RNA-derived retroposing monomeric element.
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  • 5
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 3-Hydroxy-3-methylglutaryl coenzyme A lyase (HL) is a homodimeric mitochondrial matrix enzyme that catalyzes the last step of ketogenesis. Using a human HL cDNA as a probe, we isolated a 1.4-kb mouse HL cDNA (HLM) from a mouse liver library and extended the sequence in the 5′ direction, using RACE PCR to include the complete coding sequence. The nucleotide sequence of the mouse HL coding region is 85.7% identical to human HL, and 52.6% to Ps. mevalonii HL. Peptide identities of 87.4% and 54.3% respectively were observed. Southern analysis of 29 strains of laboratory mice and of Mus spretus revealed a total of about 25 kb of hybridizing fragments and three polymorphic fragments in both EcoRI and HindIII digestions. The mouse HL locus (Hmgcl) was localized on Chromosome (Chr) 4: Pmv-19-12.6±3.6 cM-Hmgcl-7.3±2.3 cM-Xmv-8-1.5±1.0 cM-Gpd1. The human HL locus (HMGCL) was mapped to distal Chr 1p by analysis of a human-hamster hybrid cell panel and by in situ hybridization.
    Type of Medium: Electronic Resource
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