While both muscle and structure are important to
provide support and
movement to the
dogs, the metabolic system also has equal importance
in relation to movement. Its chemical reaction,
which occurs in all living organisms generates
energy and maintains life. Due to the extremely
heterogeneous tissue of the mammalian skeletal
muscle, its different muscle fibres can
metabolically satisfy various functional demands.
The Siberian Husky is an example of this. The
Siberian Husky is required to have an explosive
movement to start, which is provided by Type II
(fast twitch) muscle fibre, and endurance, which is
provided by Type I (slow twitch) muscle fibre.
Mitochondria are
structures within cells that convert the energy from
food into a form that cells can use. The number of
Mitochondrion depends on the biochemical metabolic
level. The
more exuberant the
metabolic activities
are, the more mitochondria there are present
in the cell.
Mitochondria can be described as "cellular power
plants" because its organic matter oxidation can
convert energy into Adenosine triphosphate (ATP).
Mitochondria have a small amount of their own DNA,
which is called as mitochondrial DNA (mtDNA). mtDNA
contains thirty-seven genes, which are essential to
normal mitochondrial function.
Oxidative
phosphorylation is defined as the process of using
oxygen and sugars to create the main energy source
of the cell, which is ATP. In order to make enzymes
in oxidative phosphorylation, instructions are given
by thirteen of mtDNA genes. The more a muscle is
capable of oxidizing organic matter into ATP, the
better the muscle will be.
M-Factor, so called
by thoroughbred breeding theorist Ken McLean, refers
to mtDNA. Biologists also discovered the following
three points in regards to
Mitochondria:
1)
They
possess their own DNA with its slightly different
genetic code. mtDNA is independent and non-Mendelian.
2)
Mitochondria can only be passed onto the next
generation by the mother. She can pass on some of
her mitochondria in the cytoplasm of the egg.
3)
The
rate of evolution of mtDNA appears to be
approximately ten times faster than that of Nuclear
DNA (i.e. DNA found in the nucleus of cells.
In reproduction,
since mitochondria are inherited only from the dam,
the dam’s egg cell will destroy the mitochondria in
mammalian sperm after fertilization.
Ken McLean believes
that in racing horse breeding, superior mitochondria
can be transmitted via direct female line for
generations. “Perhaps some race horses inherit
far superior mitochondria from their dams in direct
female-line descent. This might explain why some
families can produce a consistent number of stakes
winners.”, he wrote in Genetic Heritage.
What does M-Factor
have done with canine breeding? Because the sire
cannot pass on mtDNA to his offspring, it is
essential that breeders select a dam with a correct
musculoskeletal system. When breeders apply X-factor
theory and understand the importance of M-factor in
breeding, they can begin to structure the pedigree
and phenotype together in the hope of obtaining a quality
brood bitch for their future breeding programs.
