1965-Voice Of The Tennessee Walking Horse 1965 January Voice | Page 47

BASIC INHERITANCE
by
WALTER H. SMITH
Department of Animal Science
Kansas State University
Manhattan, Kansas
The following article is taken from the “Horse
Science Handbook” of the 1964 Horse Science School,
Dr. M. E. Ensminger, Director. It discusses, in lay­
mans terms, some of the more complicated phases
of animal reproduction so far as inheritance is con­
cerned and should be of great interest to all breeders
of Tennessee Walking Horses who desire to improve
the quality of their colts.
Animal breeding has been practiced by man
since the domestication of animals. It is one of our
old arts and new sciences in the general area of
animal production and management. The modern
laws or concepts of genetics were established in
1900 upon the rediscovery of Gregor Mendel's
work which was initially reported in 1865. The
laws of genetics apply to horses the same as for
other livestock; however the factual data for interi-
tance in horses is very limited compared to most
types of farm animals. Most desirable and undesir­
able traits observed in horses are at least influenced
by heredity; however when we observe an organ­
ism, it must be remembered that it is a complex
product of its inheritance and environment. Indivi­
dual traits within any species may vary immensely
in this regard.
The heredity possessed by a horse is the product
of equal contributions transmitted by each parent.
The mare provides the maternal environment, both
prenatal and postnatal, which has an important ef­
fect in early life and perhaps some influence
throughout life. The genetic contribution of each
parent to an offspring is identical in quantity. It
is contained in the chromosomes of the egg pro­
duced by the dam and the sperm of the male. In
this case thirty chromosomes are present in each
gamete. The hereditary units, known as genes, are
contained in the threadlike chromosomes which are
located in the nucleus of the cell. Only specialized
tissues, the germ tissue, of the testis and ovary can
produce reproductive cells.
For each chromosome transmitted by one parent
there is a corresponding chromosome transmitted
by the other parent. The pair is morphologically and
quantitatively alike, but