Studies of inheritance in guinea-pigs and rats, Issue 241 (Google eBook)

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Carnegie Institution of Washington, 1916 - Guinea pigs - 192 pages
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Page 94 - ... high degree. The far curve, on the other hand, begins at chance (5) for the youngest group and rises to 10 for the oldest group, with the intermediate age groups falling at 6 and 8. We turn now to the consideration of the relation of these experimental facts to the theoretical formulation elaborated at the beginning of this paper. It will be recalled that the implications of this theory were that the far transposition test would reveal significant differences between children of different age...
Page 187 - Offspring 1 2.51 2.05 + 1.00 + 3.00 .54 150 2 2.52 1.92 - 1.00 + 3.75 .73 471 3 2.73 2.51 + .75 + 4.00 .53 341 4 3.09 2.73 + .75 + 3.75 .47 444 5 3.33 2.90 + .75 + 4.25 .50 610 6 3.52 3.11 + 1.50 + 4.50 .49 861 7 3.56 3.20...
Page 190 - Vol. 38, No. 21, p. 603. Pearson, K., E. Nettleship, and CH Usher. 1913. A Monograph on Albinism in Man. Parts I and IV. Dulau & Co., London. Sollas, IBJ 1909. Inheritance of Color and of Supernumerary Mammae in Guinea-Pigs, with a Note on the Occurrence of a Dwarf Form. Reports to the Evol. Com. of the Roy. Soc., PROGRESSIVE EVOLUTION AND THE ORIGIN OF SPECIES1 PROFESSOR ARTHUR DENDY THE opening years of the present century...
Page 168 - DeVries and Johannsen have thought, but may be genetic also. Hence racial changes may be effected through selection by the isolation of genetic fluctuations, as well as by the isolation of mutations. Moreover, genetic fluctuation makes possible progressive change in a particular direction, repeated selection attaining results which it would be quite hopeless to seek by any other means. 2. The progeny of "mutant
Page 163 - F2 generation, but with no regression of the same sort in a second F, containing twice-extracted hooded animals. So far from observing further regression as a result of the second cross with wild rats, we have unmistakable evidence that the movement of the mean, mode and range of the hooded character has been in the reverse direction. So the hypothesis of modifying factors to account for the regression and for the progressive changes observed under selection becomes untenable. In repeating the experiment...
Page 71 - However, it seems most satisfactory to the writer to attempt to explain the results on the basis of four quantitative gradations of one factor, which determines the amount of the basic color-producing enzyme, if it is in any way possible.
Page 167 - J6995, grade + 4, generation 12. The character of her first F, descendants is shown in table 141. They consist of 5 hooded and 27 non-hooded individuals. The mean grade of the hooded young is 3.51, but the number of these young is too small to make this mean of much significance. One of the hooded young...
Page 166 - DISCUSSIONS on the grade of the grandparents, but shows no significant difference from the mean of the grandparental group (3.28). TABLE 143 Table 143 shows the classification of extracted hooded second F, young obtained from crossing first F, hooded rats (table 141) with wild rats. The hooded grandparents were themselves grandchildren of <? 6348, + 4, generation 10, on the side of both parents.
Page 63 - They can be considered a< determining a fine pattern within the individual hairs. CLASSIFICATION OF COLOR FACTORS 1. Factors which affect distribution and intensity of color, largely irrespective of the kind of color. (Act as if on enzyme I). (a) Factors which affect the distribution of color in contrast with white. (6) Factors which affect the intensity of color in all colored areas of the skin, fur and eyes. 2. Factors which affect the distribution and intensity of differentiation from yellow to...
Page 173 - ... by separating one from the other. A wild race seemed best suited for a test of this hypothesis, since it would be free from suspicion on the possible ground of harboring either the hooded pattern or its supposed modifier, which had converted the hooded pattern into the mutant. It was to be expected, if the hypothesis were correct, that the mutant character was hooded plus modifier; that then a cross with wild should produce in F2 hooded young (lacking the modifier) as well as mutants and selfs....