The melanomas in the platyfish–swordtail hybrid are produced genetically, as shown by Gordon (1951), by the interaction between the macromelanophore growth-modifying factors from the swordtail and a dominant platyfish sex-linked allele controlling the appearance and distribution of macromelanophores. The genic interaction manifests itself phenotypically in that the macromelanophores appear in the hybrid much earlier than in the normal platyfish and the growth of the pigmented cells seems relatively unchecked, resulting in hyperpigmentation of the animal and ultimately in the production of a tumour. (See Reed & Gordon (1931) and Gordon & Smith (1938) for a detailed description of the phases of tumour development.)

Copyright © 1957 The Company of Biologists Ltd.
1957
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