Explanation Of Gene Action As Related To Physiological

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"_ only a substance which can then be changed by other genes or by the products
of other genes. This results in long chains of effects or processes,
whereby the initial fertilized ovum and the surrounding nutrients ultimately
become the adult organism with its many physiological and anatomical
and behavioral characters.
Probably we never will know all the details about all the processes
between the genes and the finished characters which interest us. If we
ever do know, all that, we will also know everything about embryology,
physiology, growth, and all the other life processes_ In our actmal
breeding operations, such as selection, the choice of mates for making
progeny tests, or for perpetuating the line, etc., we necessarily must
work with the end products of the genes, rather than with the genes themselves.
Because the genes may be so remote from the end products and so
many other genes or environmental changes may intervene in the long chain
of events to alter the final results, we may nmke many mistakes in our
breeding operations, expecially if we base our decisions wholly on the
individual's own characters. No complete escape from that seems possible,
although proper use of such things as progeny testing, sib testing, etc.,
will make the errors fewer.
Chemical reactions rarely proceed perfectly linearly, either with time
or with the amount of raw _terial present. A very common type of reaction,
especially where the raw material is limited in amount and the action can
get underway quickly, is that in which the rate of change is proportional
to the amount of untransformed raw material still remaining. This gives
a curve of diminishing returns with time. %_en processes act thus, adding
twice as much catalyst would hasten the change only slightly. T_en genes
act in this way we naturally expect to find complete or nearly complete
dominance in the final character, even though the genes might show: no