Sex determination.

Bacci, Guido.

Date:: [1965]

Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Sex determination. Source: Wellcome Collection.

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intersexuality and balance theory of sex 99 F2 generation normal females and half normal and half intersexual males are obtained (Fig. 5.3). Fig. 5.3. Intersexes in reciprocal crosses between the European and Japanese races of Lymantria dispar (after Goldschmidt). Intersexes are distinguished in male and female intersexes: the intersexual XX moths with various degrees of female characters are the male intersexes and female intersexes the others. Complete sex reversal has been observed in certain crosses and series of various degrees of intersexuality can be made An interpretation of the above results has been obtained by assuming that the absolute values (or valences) of the M and F factors are such that in inter-racial crosses the M factors always prevail upon the F factors in the XX individuals and the F upon the M factors in the XY individuals. Inter¬ sexes are produced in inter-racial crosses because the M and F valences are different in the different races. The race whose males produce intersexual females in Fj, when crossed with females from another race, is the strongest and the Japanese race is the stronger, the European the weaker race in the case exemphfied in the above diagram. Therefore in Goldschmidt's interpretation both male and female factors of the Japanese race possess a higher valence than the corresponding factors of the European race. The quantitative relationship existing between F and M valences is well defined within each race and the difference between them always reaches a threshold which permits the normal development of male and female char¬ acters in XX and XY individuals. This hmiting value, or threshold, below which intersexes are originated, is called the epistatic minimum. This interpretation is essentially similar to the interpretation which was later advanced for Drosophila although in his pioneer work Goldschmidt Fa d СГ? Q 24 252: 50: 50^ 2Ъ% 25^ (Fig. 5.4).