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Mutation and evolution of microsatellites in Drosophila melanogaster (1998)

Schug, Malcolm D. ; Hutter, Carolyn M. ; Noor, Mohamed A.F. ; [et al.]

Springer

Genetica 102-103 (1998), S. 359-367

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ISSN: 1573-6857

Keywords: Drosophila ; microsatellites ; mutation rate ; recombination ; gvariation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Levels of nucleotide polymorphism in the Drosophila melanogaster genome are correlated with rates of recombination. This relationship may be due to hitchhiking of advantageous mutations (selective sweeps) or to continual removal of deleterious mutations from the genome (background selection). One test of the relative contributions of selective sweeps and background selection to the observed levels of variation in the genome of D. melanogaster is to compare levels of nucleotide variability (with a mutation rate on the order of 10-9 per nucleotide per generation) with more rapidly evolving DNA loci such as microsatellites. This test depends critically on details of the mutational process of microsatellites. In this paper, we summarize our studies of microsatellite characteristics and mutation rates in D. melanogaster. We find that D. melanogaster microsatellites are short and have a mutation rate (6.5 × 10-6 per locus per generation) several orders of magnitude lower than mammals studied to date. We further show that genetic variation at 18 dinucleotide repeat microsatellites in a population of D. melanogaster from Maryland is correlated with regional rates of recombination. These and other microsatellite data suggest that both background selection and selective sweeps may contribute to the correlation between DNA sequence variation and recombination in Drosophila.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1017083025154

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Sensitivity analysis of the non-linear dynamic viscoplastic response of 2-D structures with respect to material parameters (1995)

Kulkarni, Makarand ; Noor, Ahmed K.

Chichester [u.a.] : Wiley-Blackwell

International Journal for Numerical Methods in Engineering 38 (1995), S. 183-198

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ISSN: 0029-5981

Keywords: Sensitivity ; Non-linear dynamic response ; Viscoplasticity ; Finite elements ; Generalized plane stress ; Engineering ; Engineering General

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mathematics , Technology

Notes: A computational procedure is presented for evaluating the sensitivity coefficients of the viscoplastic response of structures subjected to dynamic loading. A state of plane stress is assumed to exist in the structure, a velocity strain-Cauchy stress formulation is used, and the geometric non-linearities arising from large strains are incorporated. The Jaumann rate is used as a frame indifferent stress rate. The material model is chosen to be isothermal viscoplasticity, and an associated flow rule is used with a von Mises effective stress. The equations of motion emanating from a finite element semi-discretization are integrated using an explicit central difference scheme with an implicit stress update. The sensitivity coefficients are evaluated using a direct differentiation approach. Since the domain of integration is the current configuration, the sensitivity coefficients of the spatial derivatives of the shape functions must be included. Numerical results are presented for a thin plate with a central circular cutout subjected to an in-plane compressive loading. The sensitivity coefficients are generated by evaluating the derivatives of the response quantities with respect to Young's modulus, and two of the material parameters characterizing the viscoplastic response. Time histories of the response and sensitivity coefficients, and spatial distributions at selected times are presented.

Additional Material: 8 Ill.