By using a bit-string model of evolution, we find a successful route to diploidy and sex in simple organisms. Allowing the sexually reproducing diploid individuals to also perform mitosis, as they do in a haploid-diploid cycle, leads to the complete takeover of the population by sexual diploids. This mechanism is so robust that even the accidental conversion and pairing of only two diploids giv...

Genet ic algor ithms (GAs) continue to receive increased attention as general-p ur pos e met hods for search and optimization . GAs are attrac t ive for search in complex spaces where the fun ction al relati onsh ips between paramet ers and ob jective function values are of unknown , arb itrary mat hemati cal charac te r. Desp ite t heir generally robust character, typical GAs are known to fare...

The deoxyribonucleic (DNA) content was measured by microspectrophotometry in 100 specimens from 60 patients with ulcerative colitis, including six patients in whom the colitis was associated with carcinoma. Some 23 of 30 (77%) specimens of dysplastic tissue showed aneuploidy or polyploidy, whereas 50 of 53 (94%) specimens of non-dysplastic tissue showed diploidy. The difference was statisticall...

Computer experiments that mirror the evolutionary dynamics of sexual and asexual organisms as they occur in nature, tested features proposed to explain the evolution of sexual recombination. Results show that this evolution is better described as a network of interactions between possible sexual forms, including diploidy, thelytoky, facultative sex, assortation, bisexuality, and division of lab...

Genome size, a fundamental aspect of any organism, is subject to a variety of mutational and selection pressures. We investigated genome size evolution in haploid, diploid, and tetraploid initially isogenic lines of the yeast Saccharomyces cerevisiae. Over the course of approximately 1,800 generations of mitotic division, we observed convergence toward diploid DNA content in all replicate lines...

Tremendous diversity exists among organisms with respect to their ploidy level, defined as the number of sets of homologous chromosomes per cell. As differences in ploidy represent a potentially major genomic change affecting the evolution of a species, it might be thought that ploidy evolution would be well understood. In fact, our knowledge is fragmentary, and there are several open questions...