D. F. Butcher

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Loss of fitness due to the accumulation of deleterious mutations appears to be inevitable in small, obligately asexual populations, as these are incapable of reconstituting highly fit genotypes by recombination or back mutation. The cumulative buildup of such mutations is expected to lead to an eventual reduction in population size, and this facilitates the(More)
In this study, computer simulation is used to show that despite synergistic epistasis for fitness, Muller's ratchet can lead to lethal fitness loss in a population of asexuals through the accumulation of deleterious mutations. This result contradicts previous work that indicated that epistasis will halt the ratchet. The present results show that epistasis(More)
We report for the first time radiation data on a radiation-hardened high-precision resolver-to-digital converter (RDC). The RDC has a maximum of 16 bits precision, and is manufactured in a total-dose hardened 0.6 /spl mu/m CMOS process. Single-event (SEL) and dose-rate latchup hardening are designed-in using guard rings and DICE latches. Our results show(More)
DNA-dependent RNA polymerase I from E. coli has been used as probe for determining the capacity of purified chromatin isolated from inbred and hybrid rats during the course of postweaning development to serve as template for RNA synthesis in vitro. An analysis of variance reveals both strain- and age-specific differences in the incorporation of [3H]UTP into(More)
Behala, a village about six miles from Calcutta, and have been treated in the Carmichael Hospital for Tropical Diseases. We have from time to time visited this settlement, as it was thought that a study of the conditions might throw some light on the transmission problem. Except that they are more sanitary, the general conditions under which these boys live(More)
Diallel crosses among four highly inbred lines of rats were made in order to evaluate their combining ability at 10 day intervals during postnatal growth. Analyses were undertaken to consider the relative magnitudes of different components of variation, including a heterotic effect, over a long developmental period. A general analysis of variance for least(More)
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