. The elements of genetics. Genetics. BREEDING SYSTEMS female parent and continues to do so generation after generation. Such is the undoubted origin of triploid apomictic "species" of plants and animals. There is, however, an omission in this account which would lead to an error if it were to go uncorrected. The pairing chromosomes in a triploid pair because they have crossed over and formed chiasmata. The sister chromatids at the second division, in a triploid as in a diploid, are therefore in part derived from partner chromo-. 3x 3x-1 Fig. 67.—Leaves of the normal triploid Taraxac
. The elements of genetics. Genetics. BREEDING SYSTEMS female parent and continues to do so generation after generation. Such is the undoubted origin of triploid apomictic "species" of plants and animals. There is, however, an omission in this account which would lead to an error if it were to go uncorrected. The pairing chromosomes in a triploid pair because they have crossed over and formed chiasmata. The sister chromatids at the second division, in a triploid as in a diploid, are therefore in part derived from partner chromo-. 3x 3x-1 Fig. 67.—Leaves of the normal triploid Taraxacum polyodon and its eight types of disomic mutants occurring as apomictic seedlings in nature. X J (after Gudjonsson, 1946). somes, they are dissimilar; their separation thus leads to the segregation of differences. The triploid egg cells of the original triploid apomict are not therefore genetically identical with it, or with one another. As compared with sexual species variation is much reduced, but it still occurs. The new apomictic species is thus often subsexual (Fig. 66). The adaptation of apomicts for fertility in Taraxacum has evidently taken the form of making the suppression of meiosis more complete and therefore more regular. Efficient meiosis so desirable in a diploid has become a mere nuisance in a triploid. Triploid apomicts, in fact, show almost complete suppression of cliromosome pairing and of the consequent reduction of number. 266. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darlington, C. D. (Cyril Dean), 1903-; Mather, Kenneth. New York : Macmillan
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