Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Effects of winter on genetic structure natural population of Drosophila melanogaster | Génét. Sél. Evol. 1985. 17 1 . 25-40 Effects of winter on genetic structure of a natural population of Drosophila melanogaster c. BIÉMONT Biologie des Populations Université Lyon 1 F 69622 Villeurbanne Summary A natural population of Drosophila melanogaster from a cellar was followed throughout the year and its genetic structure analysed by a sib-mating approach based on distributions of viability ratio in sib-mating offspring and enzymatic polymorphism. Flies found early in spring that had resisted cold temperature and food shortage during winter were free of deleterious factors no inbreeding depression was observed in the viability of their immediate descendants. In contrast a population established during winter in a bucket of ripe fruit placed in the cellar showed a high frequency of lethals. In both cases the increasing effective size that followed the return of a favorable environment was associated with an inbreeding depression in further generations. The collected flies were highly heterozygous at enzyme loci although the pattern was perturbed by drift and sampling error. The genetic structure of the populations may thus depend not only on effective population size but also on selection favoring heterozygotes either free of or bearing lethals according to the conditions encountered . The observation of an annual cycle of change in enzymatic and deleterious allele frequencies and degree of heterozygosity depends then on when and how flies are collected. Key words Natural population genetical structure inbreeding natural selection D. melanogaster. Resume Effets de I hiver sur la structure génétique d une population naturelle de Drosophila melanogaster Une population naturelle de Drosophila melanogaster d une cave fut suivie tout au long d une ãnnée. Sa structure génétiquê fut approchee par 1 analyse de la viabilité après croisements frère-sceur une mesure du fardeau génétique et le polymorphisme enzy-matique. Les mouches de printemps qui avaient résisté à 1 .
