Definitions of the term 'gene' typically superimpose molecular genetics onto Mendelism. What emerges are persistent attempts to regard the gene as a 'unit' of structure and/or function, language that creates multiple meanings for the term and fails to acknowledge the diversity of gene architecture. I argue that coherence at the molecular level requires abandonment of the classical unit concept and recognition that a gene is constructed from an assemblage of domains. Hence, a domain set (1) conforms more closely to empirical evidence for genetic organization of DNA regions capable of transcription and (2) has ontological properties lacking in the traditional unit definition.

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Breeding colonies of squirrel monkeys in zoos are often a mix of Saimiri taxa, which leads to the possibility of hybridization, loss of classification features, and possible reduction of fertility among hybrids. Two zoos, Potawatomi and Brookfield, were used to assess chromosomal composition of colonies. Chromosomes were analyzed from lymphocyte cultures and animals were classified into cytogenetic types. At both zoos there was a predominance of Peruvian types, but hybrids (PeruviadColombian) at Potawatomi and (Peruvian/Colombian and PeruviadGuyanan) at Brookfield were also identified. Analysis of the Brookfield lineage (three generations) revealed karyotypic Peruvians derived from hybrid parents. The Gothic versus Roman arch of periocular white hair shows intermediate or quite variable expression in hybrids and offspring derived from hybrids. Given the relative length of both pericentric inversions and the segments distal to each, a detectable reduction in fertility is predicted when compared with similarsized inversions in humans. Somatic segregation of inversion heterozygotes, which would reconstitute homozygosity and elevate fertility, was not detected.

Egg cannibalism by antennapedia and wide-type larvae of Tribolium castaneum was analyzed for two age groups (14 and 15 days old) with egg densities of 100 and 400. The effects of larval density and egg genotype (+ or ap) were also analyzed. The + larva consumed more eggs than ap larvae at both ages for the egg densities tested. Both strains were more cannibalistic at 14 days, consumed a higher percentage of eggs when egg density was increased among 14-day larvae, and tended to consume slightly more eggs of the opposite genotype when they were provided independently. However, neither strain discriminated between eggs of differing genotype when both were provided simultaneously. Egg cannibalism of the + strain increased when both genotypes of eggs were available. Reciprocal F1 hybrid larvae were similar in cannibalistic ability to the strain which served as a male parent. Larvae from "F2 recovered" ap beetles cannibalized fewer eggs than either original strain or the heterozygotes, further implicating the possible pleiotropic effect of the ap mutation on egg cannibalism.

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