. Biology and human life. Biology. Qi e--. Fig, 215. The law of segregation A hybrid produces germ cells of two kinds with respect toapairof contrasting characters—one kind bearing the elements needed for developing the dominant charac- ter, and the other kind bearing the elements that result in the re- cessive. If two individuals, A and yellows which upon self-pollenation yield yellow-seeded plants that bear yellow-seeded offspring are also pure. These lines are shown in the table by being printed in capital let- ters. In each generation, then, some of the apparently dominanj: plants will beh
. Biology and human life. Biology. Qi e--. Fig, 215. The law of segregation A hybrid produces germ cells of two kinds with respect toapairof contrasting characters—one kind bearing the elements needed for developing the dominant charac- ter, and the other kind bearing the elements that result in the re- cessive. If two individuals, A and yellows which upon self-pollenation yield yellow-seeded plants that bear yellow-seeded offspring are also pure. These lines are shown in the table by being printed in capital let- ters. In each generation, then, some of the apparently dominanj: plants will behave like hybrids and split up again when they reproduce; one out of every three dominants will turn out to be a pure dominant; and the recessives will remain pure, or capable of reproducing their characters. An attempt to explain how this seg- regation is brought about during re- production is illustrated in Fig. 215. This explanation was not known to Men- del but has been worked out since his time by careful experiments with plants and animals and by studies of the changes which take place in the cells at the time the germ cells (gametes) are formed, at the time of fertilization, and in later development. 374. Combinations of characters. In the meantime we must not for- get that every organism is made up of many characters. After showing B. both hybrid and both showing the dominant character, are mated, they may give rise to three kinds of offspring. The germ cells given off by A are of two kinds, Cg and a^ having the factor for dominance, while a-^ and a^ bear the factor for recessiveness. In the same way, B bears two kinds of germ cells. The two kinds of eggs can combine with the two kinds of sperms in four ways: (i) a recessive egg combines with a recessive sperm; (2) a recessive egg combines with a dominant sperm; (3)3 dominant egg combines with a recessive sperm; (4) a dominant egg combines with a dominant sperm. As a result, half the offspring are again hybrid and the
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