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71.
INTRoDUCTIoNlYho1iumrePensL,whiteclover,isaneconomicallyimportantplantspeciesintemperatepastures.Asbrieflyreportedby[1],ithas16pairsofchromosomes(2n=32).Asyet,nodetailedcytologicalexaminationofthisspecies,suchasC-banding,hasbeenrep0rted.Inthelastdecade,thetechnique0fC-bandinghasbeenusedt0examinehighlyrepeatedsequencesinplantchrom0s0mesandhasprovidedausefultoolf0rtheanalysis0fcyt0geneticstructureincr0pplants[2-71.Inplants,thechr0m0s0mall0calizationofhighlyrepeatedDNAsequencesbyinsituhybr… 相似文献
72.
The period (per) locus has received much attention in molecular evolution
studies because it is one of the best studied "behavioral genes" and
because it offers insight into the evolution of repetitive sequences. We
studied most of the coding region of per in Drosophila willistoni and
confirmed previously observed patterns of conservation and divergence among
distantly related species. Five regions are so highly diverged that they
cannot be aligned, whereas a region encompassing the PAS domain is very
conserved. Structural and nucleotide polymorphism patterns in the
willistoni group are not the same as those observed in previously studied
species. We sequenced the region homologous to the highly polymorphic
threonine-glycine repeat of D. melanogaster in multiple strains of D.
willistoni, as well as in other members of willistoni group, and found an
unusual amount of conservation in this region. However, the next
nonconserved region downstream in the sequence is quite variable and
polymorphic for the number of repeated glycines. The glycine codon usage is
significantly different in this glycine repeat as compared to other parts
of the gene. We were able to plot the directionality of change in the
glycine repeat region onto a phylogeny and find that the addition of
glycines is the general trend with the diversification of the willistoni
group.
相似文献
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The authors have investigated the electrical activity of corpus cavernous, first according to Wagner and Gerstenberg’ method, then, since one year, according to Stief method, in the basal state and following intracavernosal injection of vasoactive agents, or following various stimulation tests. They have found again the electrical activity described by these authors, but have been confronted with the difficulty in quantifying the data. Specially single potential analysis seems to them little reliable and reproducible for an objective interpretation. At this stage of their experience, they test two simpler criteria interpretation: the richness of the electrical activity, and the reactivity of the recording to various stimulations. Their preminary results suggest a correlation between those criteria and the state of the autonomic nervous system of the penis. 相似文献
76.
Complete sequences of the rRNA genes of Drosophila melanogaster 总被引:19,自引:0,他引:19
In this, the first of three papers, we present the sequence of the
ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of
D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S
(123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat
of D. melanogaster is AT rich (65.9% overall), with the spacers being
particularly AT rich. Analysis of DNA simplicity reveals that, in contrast
to the intergenic spacer (IGS) and the external transcribed spacer (ETS),
most of the rRNA gene regions have been refractory to the action of
slippage-like events, with the exception of the 28S rRNA gene expansion
segments. It would seem that the 28S rRNA can accommodate the products of
slippage-like events without loss of activity. In the following two papers
we analyze the effects of sequence divergence on the evolution of (1) the
28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary
structures among eukaryotic species, respectively. Our detailed analyses
reveal, in addition to unequal crossing-over, (1) the involvement of
slippage and biased mutation in the evolution of the rDNA multigene family
and (2) the molecular coevolution of both expansion segments and the
nucleotides involved with compensatory changes required to maintain
secondary structures of RNA.
相似文献
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Landscape and Climatic Variations Shaped Secondary Contacts amid Barn Owls of the Western Palearctic
Tristan Cumer Ana Paula Machado Guillaume Dumont Vasileios Bontzorlos Renato Ceccherelli Motti Charter Klaus Dichmann Nicolaos Kassinis Rui Loureno Francesca Manzia Hans-Dieter Martens Laure Prvost Marko Rakovic Inês Roque Felipe Siverio Alexandre Roulin Jrme Goudet 《Molecular biology and evolution》2022,39(1)
The combined actions of climatic variations and landscape barriers shape the history of natural populations. When organisms follow their shifting niches, obstacles in the landscape can lead to the splitting of populations, on which evolution will then act independently. When two such populations are reunited, secondary contact occurs in a broad range of admixture patterns, from narrow hybrid zones to the complete dissolution of lineages. A previous study suggested that barn owls colonized the Western Palearctic after the last glaciation in a ring-like fashion around the Mediterranean Sea, and conjectured an admixture zone in the Balkans. Here, we take advantage of whole-genome sequences of 94 individuals across the Western Palearctic to reveal the complex history of the species in the region using observational and modeling approaches. Even though our results confirm that two distinct lineages colonized the region, one in Europe and one in the Levant, they suggest that it predates the last glaciation and identify a secondary contact zone between the two in Anatolia. We also show that barn owls recolonized Europe after the glaciation from two distinct glacial refugia: a previously identified western one in Iberia and a new eastern one in Italy. Both glacial lineages now communicate via eastern Europe, in a wide and permeable contact zone. This complex history of populations enlightens the taxonomy of Tyto alba in the region, highlights the key role played by mountain ranges and large water bodies as barriers and illustrates the power of population genomics in uncovering intricate demographic patterns. 相似文献
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