Wednesday, April 8, 2009

A novel inheritance mechanism that does not fit to the second Mendelian law

Juan J. Conrado and Gregori Marañó
Universidad Popular de la Valldigna, Benifairó, Spain

Mendel´s laws are the foundation of modern genetics and the basis to understand the inheritance of single characters in peas. Here, we have attempted to verify the two major Mendel´s laws with true-breeding varieties of mediterranean orange (Citrus sinensis) and wild blueberry (Vaccinium corymbosum), using in vitro pollen-microinjection and colorimetric techniques. The offspring obtained after crossing of homozygous oranges and blueberries (F1 generation) displayed an uniform heterozygous phenotype consisting of 100% blueberries of orange color. This result is in accordance with the first Mendel´s law, and demonstrates that the blueberry character is dominant with respect to the orange character in the orange blueberry hybrids:

On the other hand, crossing of the specimens from the F1 generation produced an offspring that did not display the expected 3:1 Mendelian ratio for the F2 generation. Instead, identical proportions of oranges and blueberries were obtained in the F2, corresponding to a frequency of 1:1 in the transmission of the blueberry and orange characters. We conclude that the second Mendel´s law is not universal, and that production of oranges from orange blueberry hybrid seeds can be achieved at large scale by a novel low-cost inheritance mechanism.

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