Mendel's principles of heredity: A defenceMendel, Gregor
Science
Mendel's principles of heredity: A defence
Mendel, Gregor
Heredity; Hybridization; Mendel's law; Weldon, Walter Frank Raphael. Mendel's laws of alternative inheritance in peas
I have also noticed that a cross between a round white and a blue
wrinkled pea will in the third and fourth generations (second and third
years’ produce) at times bring forth blue round, blue wrinkled, white
round and white wrinkled peas in the same pods, that the white round
seeds, when again sown, will produce only white round seeds, that
the white wrinkled seeds will, up to the fourth or fifth generation,
produce both blue and white wrinkled and round peas, that the blue
round peas will produce blue wrinkled and round peas, but that the
blue wrinkled peas will bear only blue wrinkled seeds[126]. This
would seem to indicate that the white round and the blue wrinkled peas
are distinct varieties derived from ancestors respectively possessing
one only of those marked qualities; and, in my opinion, the white
round peas trace their origin to a dwarfish pea having white flowers
and round white seeds, and the blue wrinkled varieties to a tall
variety, having also white flowers but blue wrinkled seeds. It is
also noticeable, that from a single cross between two different peas
many hundreds of varieties, not only like one or both parents and
intermediate, but apparently differing from either, may be produced
in the course of three or four years (the shortest time which I have
ascertained it takes to attain the climax of variation in the produce
of cross-fertilised peas, and until which time it would seem useless
to expect a fixed seedling variety to be produced[127]), although a
reversion to the characters of either parent, or of any one of the
ancestors, may take place at an earlier period.
[126] If we were obliged to suppose that this is a matured conclusion
based on detailed observation it would of course constitute the most
serious “exception” yet recorded. But it is clear that the five
statements are not mutually consistent. We have dominance of round
white in first cross.
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