Selection and cross-breeding in relation to the inheritance of coat-pigments and coat-patterns in rats and guinea-pigs, Issue 70Carnegie Institution of Washington, 1907 - 50 pages |
Common terms and phrases
amount of pigmentation average grade Average number back-stripe Bateson black hooded black Irish black pigmentation blastomeres Castle cent classes coat-pattern color-pattern condition cross-breeding discontinuous variations distribution of pigment Doncaster Dutch-marked ancestry Dutch-marked animal Dutch-marked series ectoderm epidermis extent Fritz Müller gametes gray Irish group D2 group H guinea-pigs of group head spots homozygous hooded and Irish hooded individuals hooded offspring hooded pattern hooded rats indicate inheritance in group Irish pattern Irish rats Location of spots males Mendelian MENDELIAN INHERITANCE modal neural plate nose-spot young number of spots number other spots observations occur pair parents partial albino pigment spots pigmented areas primitive streak produced regression result rodents rump spots Series H shoulder spots showing spot inheritance side spots spots and total spots are inherited spots borne spotted guinea-pigs Standard deviation table 15 table 28 total albinism Total number Total other spots variation curve Vries W. E. CASTLE wide-striped
Popular passages
Page 2 - ... ordinary fluctuating variations. For mutations are permanent ; variations are transitory. A moment's reflection will indicate the probable reason. Variations which are distributed symmetrically about a modal condition, so as to produce when graphically expressed a frequency of error curve, represent the result of a number of causes acting independently of each other. These causes are principally external, consisting in varying conditions of food supply, temperature, density, moisture, light,...
Page 32 - ... varies considerably ; it may be broad, sometimes spreading out irregularly, it may be narrow and even, and in other cases it is broken into a series of spots. Very rarely it is quite absent. When the white patch of types 2 or 6 is very large, the animal approaches the darkest form of types 3 and 5, but only once have I had any hesitation in classing a rat as belonging to one or the other.
Page 31 - ... be qualified. The final result will depend upon the amount and the persistency of the regression. In DeVries's experiments with maize, as in those of Fritz Miiller ('86), the regression grows less with each selection. If this continued, the regression should ultimately become a negligible quantity. After repeated selection for a desired extreme condition, the race should become stable at a condition only a little less extreme than that selected. De Vries's fine series of selection experiments...
Page 32 - Again, though the inheritance is clearly Mendelian, when hooded and Irish rats are crossed, the gametes formed by cross-breds are not pure, but modified, each extracted pattern being changed somewhat in the direction of that pattern with which it was associated in the cross-bred parent.
Page 3 - Vries maintains that all species-forming variations are of this sort; that selection is unable to form new species, because it can neither call into existence mutations nor permanently modify a race by cumulation of abmodal fluctuations. Darwin, on the other hand, and the great majority of his followers, while admitting that races are occasionally produced by discontinuous or "sport...
Page 48 - I'h6re<lit£ de la pigmentation chez les souris. Arch. Zool. Expe>. et Gen., Ser. 3, Tom.
Page 20 - This result shows the entire inefficiency of selection in guinea-pigs to fix a coat-pattern which is dependent upon the distribution of pigment in particular spots upon the body.