What's all this about genetics? : An explanation of inheritance in plants and animals, including man himself, for the ordinary reader / [Rona Hurst].

  • Hurst, Rona, 1897-1980.
Date:
1951]
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: What's all this about genetics? : An explanation of inheritance in plants and animals, including man himself, for the ordinary reader / [Rona Hurst]. Source: Wellcome Collection.

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    THE BIRTH OF GENETICS 21 or mother parent, whichever way the cross had been made. Satisfied on this point, Mendel now took the first- generation crossbreds and allowed them to self-fertilize. Each of the plants in the second generation produced peas of two colours, yellow or green, thus proving that the first crossbred yeUow peas carried the green colour without showing it; in other words, the ycUow colour was dominant over the green, which was termed recessive. Going on to the next generation, Mendel found that the green-seeded peas bred absolutely true, in spite of the fact that their parents had appeared to be yellow. No matter how many generations were sown, the yellow never appeared again; it had been completely thrown out. But the tale of the yellow-seeded peas in the third generation was very different. While a part of the yellow peas bred absolutely true, in the same way as the green peas, the rest of the yellows always behaved in the same manner as the original crossbreds, throwing pure yellows, pure greens, and the impure yellows, which would repeat the mixture again. There was no means of telling the pure yellows from the impure yellows except by breeding, but the greens could always be relied on to give nothing but green. The purity of the extracted yellows and greens was a startling discovery in face of the current belief in the complete fusion of maternal and paternal characters, and formed the basis of what was to become known as the Mendelian Principles of Heredity. Having got so far, Mendel began to add up his numbers, which disclosed another surprising fact. The two colours were segregating out in a perfecdy regular way, in the ratio of one pure yellow and two impure yellows to one pure green, or three (apparent) yellows