There are many slight deviations, however, and no consensus exists on the origin of Zipf's Law.
Despite extensive clinical and fundamental research, controversy still exists on the origin of serous female adnexal tumors.
The economic importance of ore deposits has ensured their thorough study by all techniques of geological and geochemical research, but much controversy still exists regarding the origin of many of the more complex deposits.
Diarrhea is a major cause of illness and death in Iraqi children; however, little information exists about the origin of childhood diarrhea.
This suggests that the new MCM-DNA crystal structure reported by Froelich, Kang et al. might have captured an intermediate form of DNA that exists when the origin of replication melts at the onset of DNA replication.
In all of these hospital outbreaks, the potential for contamination of hospital sources and equipment by infected patients or other environmental sources (such as dust or dirt) exists; hence the origin of the culprit strain remains unclear.
It is worthwhile to note that a parallel argument exists regarding the origin of mammalian isochores: Fryxell and Zuckerkandl (2000) hypothesized that the mutagenetic property of DNA methylation and its relationship to DNA melting can explain the evolution of isochores in warm-blooded vertebrates.
In fact, the number of subfamilies that existed before the origin of metazoans may be underestimated by these analyses, given that it is possible that the lineage that gave rise to the single choanoflagellate analyzed lost some HECT genes.
Countless stories exist concerning the origin of peculiar rocks, properties of animals, plants, stars, or other features in the world.
Microbe-plant interactions have existed since the origin of plants, and microbes have been demonstrated to contribute to all major aspects of plant life, including regulation of metabolism and growth, nutrient acquisition and resistance to biotic and abiotic stressors1,2.
