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The chicken embryo is a unique model that overcomes many limitations to studying the biology of cancer in vivo. The chorioallantoic membrane (CAM), a well-vascularized extra-embryonic tissue located underneath the eggshell, has a successful history as a biological platform for the molecular analysis of cancer including viral oncogenesis, [8] carcinogenesis, [9] tumor xenografting, [1] [10] [11 ...
He questioned how chickens fed a diet of oats could produce eggshells composed of calcium carbonate and concluded that the potassium in the oats must combine with hydrogen to produce the calcium. [3] He considered this a "low-energy transmutation" which became known as the "Kervran effect". There is no scientific basis for such an effect. [3]
Instead of silencing the entire chromosome as humans do, male chickens (the model ZZ organism) seem to engage in selective Z silencing, in which they silence only certain genes on the extra Z chromosome. [35] [36] Thus, male chickens express an average of 1.4-1.6 of the Z chromosome DNA expressed by female chickens. [37]
The balance of nature, also known as ecological balance, is a theory that proposes that ecological systems are usually in a stable equilibrium or homeostasis, which is to say that a small change (the size of a particular population, for example) will be corrected by some negative feedback that will bring the parameter back to its original "point of balance" with the rest of the system.
SF Gilbert, JM Opitz, and RA Raff. 1996. "Resynthesizing Evolutionary and Developmental Biology". Developmental Biology. 173:357-372; G von Dassow and E Munro. "Modularity in Animal Development and Evolution: Elements of a Conceptual Framework for EvoDevo". J. Exp. Zool. 285:307-325. MI Arnone and EH Davidson. 1997.
The best-known homeostatic mechanisms in humans and other mammals are regulators that keep the composition of the extracellular fluid (or the "internal environment") constant, especially with regard to the temperature, pH, osmolality, and the concentrations of sodium, potassium, glucose, carbon dioxide, and oxygen.
A well-studied case is that of sickle cell anemia in humans, a hereditary disease that damages red blood cells. Sickle cell anemia is caused by the inheritance of an allele (HgbS) of the hemoglobin gene from both parents. In such individuals, the hemoglobin in red blood cells is extremely sensitive to oxygen deprivation, which results in ...
The Breland's described their first exposure to this phenomenon when working with their chickens that had been trained to appear as if they were turning on a jukebox and subsequently dancing. The breakdown in operant conditioning appeared when over half the chickens they had trained to stand on a platform developed an unplanned scratching or ...