資料來源 : Webster's Revised Unabridged Dictionary (1913)
Mendel's law \Men"del's law\
A principle governing the inheritance of many characters in
animals and plants, discovered by Gregor J. Mendel (Austrian
Augustinian abbot, 1822-84) in breeding experiments with
peas. He showed that the height, color, and other characters
depend on the presence of determinating factors behaving as
units. In any given germ cell each of these is either present
or absent.
Note: The following example (using letters as symbols of the
determining factors and hence also of the individuals
possessing them) shows the operation of the law:
Tallness being due to a factor T, a tall plant, arising
by the union in fertilization of two germ cells both
bearing this factor, is TT; a dwarf, being without T,
is tt. Crossing these, crossbreeds, Tt, result (called
generation F_{1}). In the formation of the germ cells
of these crossbreeds a process of segregation occurs
such that germ cells, whether male or female, are
produced of two kinds, T and t, in equal numbers. The T
cells bear the factor ``tallness,'' the t cells are
devoid of it. The offspring, generation F_{2}, which
arise from the chance union of these germ cells in
pairs, according to the law of probability, are
therefore on an average in the following proportions: 1
TT : 2 Tt : 1 tt; and thus plants pure in tallness (TT)
and dwarfness (tt), as well as crossbreeds (Tt), are
formed by the interbreeding of crossbreeds. Frequently,
as in this example, owning to what is called the
dominance of a factor, the operation of Mendel's law
may be complicated by the fact that when a dominant
factor (as T) occurs with its allelomorph (as t),
called recessive, in the crossbreed Tt, the individual
Tt is itself indistinguishable from the pure form TT.
Generation F_{1}, containing only the Tt form, consists
entirely of dominants (tall plants) and generation
F_{2} consists of three dominants (2 Tt, 1 TT) to one
dwarf (tt), which, displaying the feature suppressed in
F_{1}, is called recessive. Such qualitative and
numerical regularity has been proved to exist in regard
to very diverse qualities or characters which compose
living things, both wild and domesticated, such as
colors of flowers, of hair or eyes, patterns,
structure, chemical composition, and power of resisting
certain diseases. The diversity of forms produced in
crossbreeding by horticulturists and fanciers generally
results from a process of analytical variation or
recombination of the factors composing the parental
types. Purity of type consequently acquires a specific
meaning. An individual is pure in respect of a given
character when it results from the union of two sexual
cells both bearing that character, or both without it.
資料來源 : WordNet®
Mendel's law
n : (genetics) one of two principles of heredity formulated by
Gregor Mendel on the basis of his experiments with
plants; the principles were limited and modified by
subsequent genetic research