Gametic Phase Disequilibrium

2008 ◽  
pp. 1200-1200
Keyword(s):  
Gametic Phase Disequilibrium ◽  
Gametic Phase

scholarly journals A class of population genetic questions formulated as the generalized occupancy problem.

Genetics ◽  
1993 ◽  
Vol 134 (3) ◽  
pp. 953-958
Author(s):  
R Chakraborty
Keyword(s):  
Induced Mutations ◽  
Global Test ◽  
Sampling Distributions ◽  
Genotype Frequencies ◽  
Occupancy Problem ◽  
Multinomial Probabilities ◽  
Genetic Data Analysis ◽  
Restriction Site Polymorphisms ◽  
Gametic Phase Disequilibrium ◽  
Gametic Phase

Abstract In categorical genetic data analysis when the sampling units are classified into an arbitrary number of distinct classes, sometimes the sample size may not be large enough to apply large sample approximations for hypothesis testing purposes. Exact sampling distributions of several statistics are derived here, using combinatorial approaches parallel to the classical occupancy problem to help overcome this difficulty. Since the multinomial probabilities can be unequal, this situation is described as a generalized occupancy problem. The sampling properties derived are used to examine nonrandomness of occurrence of mutagen-induced mutations across loci, to devise tests of Hardy-Weinberg proportions of genotype frequencies in the presence of a large number of alleles, and to provide a global test of gametic phase disequilibrium of several restriction site polymorphisms.

scholarly journals MULTILOCUS STRUCTURE OF NATURAL POPULATIONS OF HORDEUM SPONTANEUM

Genetics ◽  
1980 ◽  
Vol 96 (2) ◽  
pp. 523-536 ◽  
Author(s):  
A H D Brown ◽  
M W Feldman ◽  
E Nevo
Keyword(s):  
Wild Barley ◽  
Natural Populations ◽  
Hordeum Spontaneum ◽  
Wild Populations ◽  
Allozyme Data ◽  
Complete Independence ◽  
Esterase Loci ◽  
Cultivated Barley ◽  
Gametic Phase Disequilibrium ◽  
Gametic Phase

ABSTRACT The association of alleles among different loci was studied in natural populations of Hordeum spontaneum, the evolutionary progenitor of cultivated barley. The variance of the number of heterozygous loci in two randomly chosen gametes affords a useful measure of such association. The behavior of this statistic in several particular models is described. Generally, linkage (gametic phase) disequilibrium tends to increase the variance above the value expected under complete independence. This increase is greatest when disequilibria are such as to maximize the sum of squares of the two-locus gametic frequencies.—When data on several loci per individual are available, the observed variance may be tested for its agreement with that expected under the hypothesis of complete interlocus independence, using the sampling theory of this model. When applied to allozyme data from 26 polymorphic populations of wild barley, this test demonstrated the presence of geographically widespread multilocus organization. On average, the variance was 80% higher than expected under random association. Gametic frequencies for four esterase loci in both of these populations of wild barley and two composite crosses of cultivated barley were analyzed. Most generations of the composites showed less multilocus structure, as measured by the indices of association, than the wild populations.

scholarly journals Number of recombinations and genetic properties of a maize population undergoing recurrent selection

2009 ◽  
Vol 66 (1) ◽  
pp. 52-58 ◽  
Author(s):  
Francisco Pinheiro Lima Neto ◽  
Cláudio Lopes de Souza Júnior
Keyword(s):  
Genetic Variability ◽  
Grain Yield ◽  
Recurrent Selection ◽  
Genetic Correlations ◽  
Selection Cycle ◽  
Genetic Variances ◽  
Maize Population ◽  
Two Generations ◽  
Gametic Phase Disequilibrium ◽  
Gametic Phase

In maize recurrent selection programs, selected genotypes were recombined once to generate genetic variability for the next selection cycle. Selection generates negative gametic phase disequilibrium which reduces genetic variances, and this disequilibrium is not significantly reduced with only one generation of recombination. The objective of this research was to assess the effects of one additional generation of recombination on phenotypic and genotypic parameters in a maize population undergoing recurrent selection. Selected progenies of the EPB-4 population were subjected to one and two generations of recombination, and from each generation half- and full-sib progenies were developed and evaluated at three environments for grain yield, plant and ear heights, prolificacy, and ear placement. There were no significant changes between each progeny type with one and two generations of recombination for the means, ranges, phenotypic distribution of the traits, genetic variances, heritability coefficients, and genetic correlations for the traits assessed. The results suggest that an additional generation of recombination will not increase the effectiveness of maize recurrent selection programs.

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