New paths in genetics / by J.B.S. Haldane.

  • J.B.S. Haldane
Date:
1941
Catalogue details

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

Credit: New paths in genetics / by J.B.S. Haldane. Source: Wellcome Collection.

    93/216 page 89
    Genetics and Development there is not complete agreement as to which hormones are present, nor will there be until the hormones of this gland have been definitively separated. There is a possi¬ bility that the eosinophil cells, which are completely absent in the dwarf pituitaries, are diminished in number in the heterozygotes. The normal allelomorph of the gene for dwarfism is presumably responsible for the development of the eosinophil cells, and the production of a group of hor¬ mones. In every other cell of the body this gene would seem to be inactive, or at any rate to be of no great importance. There is nothing surprising in this. Genes are known in Drosophila which affect a single pair of bristles. But as this gene for non-dwarfism happens to be essential for a key group of cells, the effects of muta¬ tion spread to every organ of the body. In Drosophila melanogaster a lethal recessive gene produces giant larvae which do not metamorphose, but carry out an extra moult, and then die. There is also a giant race, differing from the normal in respect of two genes, in which an extra larval moult occurs before metamorphosis. These forms seem to be due to hormonic abnormalities, but in view of the rather complex relation between moulting and metamorphosis in Hemiptera it is too early to say just what hormonic abnormality occurs in them. It is possible, and indeed probable, that genes exist which produce smaller changes in the activity of various 89
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