Alex Fraser

Neurological Defect: Manganese in Phenocopy and Prevention of a Genetic Abnormality of Inner Ear

A specific congenital ataxia may be caused by presence of mutant genes and by manganese deficiency during prenatal development in normal mice. Supplementation of the diet of mutant mice with manganese during prenatal development rectifies the aberrant development, resulting in normal behavior. The congential ataxa results from defective development of the the otoliths.

Simulation of genetic systems X. Inversion polymorphism

Abstract The effects of normalizing selection on populations containing inversions has been simulated for a six locus genetic model. The results show that co-adaptation to form a stable inversion polymorphism will only occur if the inversion is introduced at a frequency greater than 0·12. Over-dominance has been shown not to be a necessary feature of inversion polymorphism. The accession to stable polymorphism involves a newly-formed inversion having an additive advantage which is sufficient to result in an increase in frequency up to 12%, when the process of co-adaptation begins, resulting in the evolution of stable polymorphism.

Simulation of genetic systems : XI. Normalizing selection.

SummaryThe effects of intense normalizing selection have been studied, using computer simulation, for models of 3, 4, 5, 6, 8, 12 and 24 loci. The effectiveness of such selection in reducing heterozygosity decreases with increase of the number of loci to a limit that is only slightly greater than that consequent from random genetic dispersion, if the loci are freely recombining. Tight linkage markedly reduces the rate of loss of heterozygosity for small numbers of loci, but this effect of tight linkage decreases with increase of the number of loci.ZusammenfassungEs wird die Wirkung normalisierender Selektion für 3, 4, 5, 6, 8, 12 und 24 Loci unter Verwendung von Computer-Simulationen untersucht. Die Wirksamkeit derartiger Selektion hinsichtlich der Reduzierung der Heterozygotie nimmt mit zunehmender Zahl der Loci bis zu einem Grenzwert ab, der nur größer ist als der aus zufällinger genetischer Dispersion folgende, wenn die Loci frei miteinander Rekombinieren. Enge Koppelung reduziert die Rate des Heterozygotenverlustes bei kleiner Zahl von Loci beträchtlich, jedoch nimmt dieser Effekt der engen Koppelung mit steigender Zahl der Loci ab.