1,721,101 research outputs found
Development of insecticide resistance in Piophila casei (Diptera: Piophilidae) strains selected with low doses of deltamethrin
No full textTwo populations of the cheese skipper, Piophila casei (L.), were sampled. The 1st was from a sheep farm where no chemical was ever applied; the 2nd was present in a ham factory where chemical treatment with pyrethroids was applied in the past against house flies, Musca domestica L., and Dermestid beetles. A substantial difference between their resistance to deltamethrin was observed (LC(50) = 11.56 versus 68.08 mu g/cm(2) for females and 1.11 versus 4.20 mu g/cm(2) for males, respectively). Laboratory strains were established from both populations and were selected at constant rates for up to 20 generations (2, 4, and 7.3 ppm for the strains derived from the 1st population and 40 ppm for that selected from the 2nd population). Males and females of both strains showed an increase in LC(50) (tested at the 5th and 19th or 10th generation), except when females were selected at the lowest rate (2 ppm). At the end of the trial, slopes of logit regressions were substantially steeper in strains selected at higher rates, suggesting that the effect of the insecticide was to reduce resistance variance. Crosses between unselected and selected strains were done. Results of survival analysis in F-1 hybrids were analogous for males and females and were similar in both reciprocal crosses. LC(50)s were intermediate between those of the parental strains
A marine host-mediated assay for the detection of mutagenic compounds in polluted sea waters
No full textGenotype probabilities of pairs of individuals for X-chromosome markers
No full textBACKGROUND: The usual set of autosomal markers (A-STRs) available in commercial kits is often insufficient to discriminate between close relationships when only two subjects are available for analysis. X-chromosome markers (X-STRs) provide higher statistical power in special cases. STUDY DESIGN AND METHODS: Formulas are derived for the probabilities of all possible genotype pairs for X-STRs of any sex combination for seven common relationships. The power of exclusion (PE) of X-STRs in parentage analysis is compared with that of A-STRs of equivalent distribution of allele frequency. RESULTS: Seventy-three equations were obtained, from which the likelihood ratio of any two alternative hypotheses about the relationship between two individuals can be obtained by division and simplification. For father-daughter and mother-son duos, the PE of X-STRs is almost twice the corresponding value of A-STRs for moderately low values of heterozygosity (0.6-0.75); for alleged pairs of sisters and pairs of half-sisters the PE is equivalent to that of A-STRs in parent-child duos. Considering four real unlinked X-STRs, the cumulative PE for father-daughter and mother-son duos was 99 percent, compared with 94 percent if they were autosomal. CONCLUSIONS: X-STRs can substantially increase the discrimination capacity of standard A-STRs in parentage analyses involving pairs of individuals. Up to four unlinked X-STRs may be treated as independent loci. When linked loci are included, computer programs that calculate pedigree likelihoods can be used
A HOST-MEDIATED ASSAY WITH MUSSELS - DETECTION OF MUTAGENIC SUBSTANCES IN THE VENICE LAGOON
No full textSTUDY METHODS FOR IDENTIFICATION OF MUTAGENIC SUBSTANCE .1. SALMONELLA-TYPHIMURIUM AS GENETIC SYSTEM FOR MOLECULAR CHARACTERIZATION OF MUTATION RESULTS
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Genetic epidemiology of colorectal cancer
No full textStarting from a survey of the studies on familiar aggregation of colorectal cancer, we introduce the aims of genetic epidemiology. One of its main goals is to assess population frequency of cancer susceptibility genes and to determine the age-specific risks for carriers with respect to non-carriers. In section two, segregation analysis investigations are reviewed, and inferences on the relevance of genetic components of susceptibility to colorectal cancer are drawn. In section three, the HNPCC paradigm is discussed in the light of the Knudson model of tumorigenesis and recent advances of molecular research. In the last section we show an example of genotype/environment interaction in the etiology of a particular cancer and present a conceptual framework for studies on cancer genetic epidemiology in terms of attributable and relative risk
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