The genetics of Paramecium aurelia / [Geoffrey Beale].

  • Beale, Geoffrey, 1913-
Date:
1954
Catalogue details

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

Credit: The genetics of Paramecium aurelia / [Geoffrey Beale]. Source: Wellcome Collection.

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    The Genetics of Paramecium aurelia leaves and flowers, loss of anthocyanin pigment, etc. In fact, almost any character of the plant may be affected. To take an example from the animal kingdom. Laven (1953) has recently reported the results of crossing different races of Culex pipiens, and found that the eggs of some races, when fertilized by the sperm of some other races, produced inviable offspring, though the reciprocal matings were quite successful. Even after fourteen generations of backcrossing (using of course the fertile combination), the cytoplasm of the race used as female parent retained its characteristic properties. It appears to be a fairly common occurrence that when the cytoplasm of one race or species of plant or animal is brought into combination with the genes of another, certain disturbances in normal development are liable to occur. Thus in a given race or species there has been a mutual adaptation of cytoplasmic and chromosomal factors. These facts, and others to be described in detail later, show that the cytoplasm possesses certain hereditary properties of its own, that is, it may behave to some extent independently of the control exerted by the genes in the chromosomes and of the ex¬ ternal environment. However, there is little or no information available concerning the nature and properties of the cytoplas¬ mic factors, comparable to that which we now possess for the genes. Among the questions which need answering are the following : ( I ) Are the cytoplasmic factors located in any known visible structures? (2) To what extent are the cytoplasmic fac¬ tors influenced by {a) the genes, and {b) the external environ¬ ment? (3) Are the cytoplasmic factors of universal occurrence, playing an essential role in the development of all organisms, or are they only of limited significance? (4) Could these pheno¬ mena be explained in some other way, dispensing altogether with the notion of autonomous cytoplasmic factors ? Some infor¬ mation bearing on these questions is available, and will be discussed later. For the moment it is safe to say that none of them has been answered clearly. 10