The Situation in Biological Science, pp. 481-482 (1948)
Oddities of Segregation
N. V. Turbin

The next group of facts shows that, under certain conditions, organisms known to be heterozygous in nature, of hybrid origin, produce a non-segregating generation, and that under other conditions, organisms that are of the homozygous genotype, of "pure" origin, can produce a segregating generation.

Further, we know of facts which show that changes in the phenotype of hybrids caused by training under definite conditions of existence, responsively affect the segregation of the sexual generation. If the development of the characters of the hybrids tends in the direction of the mother, their progeny shows a larger number of individuals possessing the corresponding characters of the mother.

If the same kind of hybrids possessing the same initial genotype are diverted by training to the side of the paternal organism, the relative number of progeny with paternal characters increases accordingly. According to the theory of the gene, however, each pair of genes must produce an equal number of gametes bearing the paternal gene and the maternal gene, irrespective of whether the maternal or paternal gene exercises predominating influence upon the development of the corresponding. characters. Thus, according to the theory of the gene, changes in the phenotype caused by the influence of conditions in which it is trained should not exercise a responsive influence on its genotype and on the segregating generation. Time will not permit me to quote facts of this kind that I and my assistants have obtained in experiments with tomatoes. Academician D. A. Dolgushin quoted similar facts when he spoke. And such facts are also quoted in some of the works of formal geneticists (Bateson, Crane, Correns, and others).

The cases Turbin alludes to may be related to Elective Expression. In such cases "dominance" is the expression of one allele, suppression of the other. This sort of dominance can be influenced by environmental conditions as well as internal factors (genotype). If the expression is altered, either by vegetative selection or by mentoring, the newly selected dominance may be transmitted to the offspring with no change in the relevant genes. Furthermore, under greatly changed conditions, heterozygotes that express only one allele may yield segregating offspring when the silencing is released.

Ford (1940) gave another example involving wing color in the current moth, Abraxas grossulariata.

Davenport (1907): Some fowl have five toes instead of the normal four. When a four- and a five-toed fowl are crossed the offspring show no blend, they are either four-toed or five-toed, and neither character dominates. If the extra toe is well developed in the parents a large percentage of the offspring have an extra toe; if the extra toe is poorly developed in the parents a small percentage of the offspring have an extra toe. In this case we have a unit character — extra toe — but no dominance or recessiveness and no evidence of pure germ-cells. The result seems to depend on the relative potency of the four-toed and the five-toed tendency.

Cook (1909) Intensification and Suppression