The Mechanism of Mendelian Heredity (Google eBook)

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H. Holt, 1915 - Chromosomes - 262 pages
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Page 43 - We must suppose, then, that the Mendelian factors are not sorted out, each to its appropriate cell, so that factors for color go only to pigment cells, factors for wing-shape to cells of the wings, etc., but that differentiation is due to the cumulative effect of regional differences in the egg and embryo, reacting with a complex factorial background that is the same in every cell.
Page 215 - These disintegrated conditions I have spoken of as subtraction or reduction stages. For example, the Picotee sweet pea, with its purple edges, can surely be nothing but a condition produced by the factor which ordinarily makes the fully purple flower, quantitatively diminished. The pied animal, such as the Dutch rabbit, must similarly be regarded as the result of partial defect of the chromogen from which the pigment is formed, or conceivably of the factor which effects its oxidation. On...
Page 252 - SHULL, GH, 1908. The Composition of a Field of Maize. Am. Breeders
Page 4 - ... receive the tall as the short. Sutton pointed out that in the same way the segregation of one pair of chromosomes is probably independent of the segregation of the other pairs. It was obvious from the beginning, however, that there was one essential requirement of the chromosome view, namely, that all the factors carried by the same chromosome should tend to remain together. Therefore, since the number of inheritable characters may be large in comparison with the number of pairs of chromosomes,...
Page 1 - Chapter I Mendelian Segregation and the Chromosomes Mendel's law was announced in 1865. Its fundamental principle is very simple. The units contributed by two parents separate in the germ cells of the offspring without having had any influence on each other. For example, in a cross between yellow-seeded and green-seeded peas, one parent contributes to the offspring a unit for yellow and the other parent contributes a unit for green. These units separate in the ripening of the germ cells of the offspring...
Page 61 - The chance that such a process of crossing over will occur between any two given points on the chromosome should obviously be greater, the greater the distance between these points. If then the Mendelian factors lie along the chromosome, the amount of crossing over between any two of them will depend on their distance apart. Should two points lie near together a crossover will only rarely occur between them; if they lie further apart the chance of such a crossover taking place at some point between...
Page 1 - ... progress of their investigations they have observed the origin of over a hundred factor-mutations in this species, and they have determined the hereditary interrelations of a large number of them. They have established, for the fruit fly, the validity of the fundamental conception of Mendelism that the units contributed by two parents separate in the germ cells of the offspring without having had any effect on one another, that long and intimate association in the same chromosomal mechanism does...
Page 1 - These units separate in the ripening of the germ cells of the offspring so that half of the germ cells are yellow bearing and half are green bearing. This separation occurs both in the eggs and in the sperm. Mendel did not know of any mechanism by which such a process could take place. In fact, in 1865 very little was known about the ripening of the germ cells. But in 1900, when Mendel's long.forgotten discovery was brought to light once more, a mechanism had been discovered that fulfils exactly...
Page viii - But it should not pass unnoticed that even if the chromosome theory be denied, there is no result dealt with in the following pages that may not be treated independently of the chromosomes; for, we have made no assumption concerning heredity that cannot also be made abstractly without the chromosomes as bearers of the postulated hereditary factors.
Page 2 - Thus the behavior of the chromosomes parallels the behavior of the Mendelian units, for in the germ cells each unit derived from the father separates from the corresponding unit derived from the mother. These units will henceforth be spoken of as factors; the two factors of a pair are called allelomorphs of each other. Their separation in the germ cells is called segregation.

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