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Pregnancy block, whereby recently mated female mice abort their pregnancies when exposed to novel (strange) males, was studied in house mice (Mus domesticus) differing in t-complex genotype; t-mutations are deleterious and +/t females avoid +/t males as mates. The results of Experiment 1, in which the genotype of the female, stud male, and strange male was systematically varied, showed that pregnancy block was most frequent when the strange male was +/+. Because this effect was not enhanced among +/t females when stud males were +/t, the results cannot clearly be explained by the hypothesis that pregnancy block is a manifestation of mate choice. Moreover, the 'strange male' effect in Experiment 1 is unlikely to be a female response correlated with the risk of male infanticide, as +/+ and +/t males did not differ in their infanticidal tendencies (Experiments 2 & 3). Alternative hypotheses, including a modified version of the mate choice hypothesis, are discussed.

Wild house mice (Mus domesticus) are commonly heterozygous (+/t) for a genetic mutation referred to as a 't-haplotype,' in the t-complex of chromosome 17. Considerable debate has been concerned with the factors controlling the frequency of heterozygotes in wild populations. However, differential trappability of heterozygous and wildtype (+/+) mice could seriously affect this estimate. We examined the relative propensity of +/t and +/+ mice to enter Sherman live traps placed in large outdoor pens. Overall, males are more likely to enter traps than are females. Additionally, more aggressive males are more likely to enter traps than are less aggressive ones. However, there was no statistically significant effect of male t-complex genotype on capture rate. In contrast, +/t females were significantly less likely to enter live traps than their +/+ counterparts. Trapping bias favoring +/+ over +/t females could result in a small (ca. 10%) underestimate of the frequency of t-haplotypes among wild mice., INTRODUCTION Worldwide, in natural populations of wild house mice (Mus domesticus) a high proportion (mean = 25%) of individuals are heterozygous (+/t) for a genetic mutation at the t-complex on [...]

A study of female mate preferences in mice indicates that the preference depends on genetically-based fitness differences. Male mice having t-haplotypes different from those of the females, attracted the females more than the other males. This also increases the production of stronger offspring which can survive in unfavorable environments.

Synopsis. This paper reviews work conducted over the last several years on the effect of genetic differences within the t-complex of wild house mice on female mating preference. Wild mice are polymorphic for a mutation within the t complex on chromosome 17. About 25% of wild mice are heterozygous (+/t) for a t-haplotype and the remainder are +/+. These t-haplotypes have a number of deleterious effects when homozygous and hence t/t individuals are rarely found in wild populations. We have examined preferences of +/+ and +/t females for males of both genotypes. We have found that +/t, but not +/+ females have strong preferences for + / + males. These preferences can be modified by a variety of factors including estrous condition of the female (the preferences are stronger among estrous than diestrous females) and the dominance status of the male (when forced to choose, females give priority to male dominance status over t complex genotype in choosing males). The restriction of preference to + /t females indicates that genes on t haplotypes modulate these preferences. Because t haplotypes include the major histocompatibility complex MHC) of the mouse we designed a study to ascertain whether the preferences of +/t females were associated with the MHC. Results of the study indicate that the preferences are independent of the MHC. Further work testing females carrying a partial t-haplotype [t.sup.w18]) indicates that the genes for mating preference are localized in the region of the t complex distal to the MHC. A large number of t haplotypes are found in wild mouse populations. Females that are themselves +/t when forced to choose between 2 +/t males (one carrying a haplotype that is the same as their own and one carrying a haplotype that is different) prefer males carrying t-haplotypes that differ from their own. Finally, we conclude that mating preference may only be a weak force regulating the frequency oft- mutations in wila mouse populations. The impact of mating preference on population genetics of genes within this region is muted because of the great importance of male dominance rank in determining mating pattems within interacting social groups.

A new postprocessing algorithm was developed for the diagnosis of breast cancer using electrical impedance scanning. This algorithm automatically recognizes bright focal spots in the conductivity map of the breast. Moreover, this algorithm discriminates between malignant and benign/normal tissues using two main predictors: phase at 5 kHz and crossover frequency, the frequency at which the imaginary part of the admittance is at its maximum. The thresholds for these predictors were adjusted using a learning group consisting of 83 carcinomas and 378 benign cases. In addition, the algorithm was verified on an independent test group including 87 carcinomas, 153 benign cases and 356 asymptomatic cases. Biopsy was used as gold standard for determining pathology in the symptomatic cases. A sensitivity of 84% and a specificity of 52% were obtained for the test group. Index Terms--Breast cancer, electrical impedance scanning, medical diagnosis, postprocessing algorithm.

Many years ago, as a beginning graduate student just getting my feet wet as a field biologist, I would sit waiting for the killdeer I was watching to attack their [...]