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Joined: March 29th, 2009, 5:01 pm
Mendels Law, by Kenny Troiano
Copyright © 2013 by Kenny Troiano/Maximus Troy
Thanks to Gregor Mendel, we now know that the structure and
makeup of all living things are the result of inheritable
characteristics. However, structures that are changed, due
to their environment after birth, are not inheritable. As a
result, a dog's tail may be cut off, but his progeny would
not consist of tailless dogs just because their parent had
his tail cut off. A cow may be dehorned, but her progeny
will not be hornless due to the fact that their mother had
her horns cut off. On the other hand, a true tailless dog or
hornless cattle are originally "sports" and are easily
explained by the laws of Mendel.
An Explanation Of Inheritance: To begin with, it is
important to understand that the inheritable factors, we
call unit characters, are transmitted through the germ
plasm. It is the microscopic granules combining the
chromosomes that transmit characteristics and traits, good,
bad, and indifferent.
In regard to reproduction, it may be said that in mammals,
where the young are depended upon the mother during the
earlier stages of their growth, the egg or germ cells are
microscopic in size and contain only a small amount of yolk,
called deutoplasm, that enables them to reach the stage at
which they develop the processes for attaching themselves to
the wall of the mother's uterus.
In birds, the contents of the egg form the source of food or
nutrients for the developing young, and this continues for
more than seventy-two hours after emerging from the shell.
Also, unlike mammals’, the chicks are very large in
comparison to the size of the parent that produced them.
In the reproduction of animals or plants there are two
sexual cells. The female cell in the animal is called ovum,
and in plants, ovule. The male element is called a
spermatozoon in the animal and pollen in the plant. These
are known as gametes.
The sexual cells of the male are very small (microscopic in
size) and are produced in the testes.
The ovum of the hen does not possess the power of movement,
while the male spermatozoa are gifted with active movement.
In birds, they take the form of a long whip, with slender
lash or filament. By aid of this flagellum they move about
in any liquid they happen to be deposited in in search of
The new individual is formed by the union or fusion (yoking
together) of a male and female gamete. This fusion is called
a zygote. Therefore the zygote is a double structure, in
which components brought in by each of the gametes remain
intimately fused in a form of partnership.
From this the life cycle of a bird may be divided into:
• First, a period of isolation in the form of a gamete, and
living as a single unit awaiting the union with the gamete
of the opposite sex, to make possible further development.
• Second, the period of union of the two gametes forming the
zygote and cell division and formation of a fully developed
Nature's system of inheritance was first worked out on
plants: Mendel crossed the tall pea (6 feet in height) on a
dwarf pea (1.5 feet high), and, although each kind of plant
had been proved to breed true to height, if they were
crossed artificially, using either as the pollen parent, the
other being used as the ovule parent, the result of crossing
tall with dwarf was, in every case, nothing but talls. This
tall character, because it dominated, was called the
dominant character. The dwarf character was called the
recessive character. The progeny in this case is the F1
Seeds from this F1 generation, produced the following year,
gave rise to talls and dwarfs with no intermediates. This
formed the F2 generation, the talls numbering three to the
dwarfs one (3 to 1 ratio).
From the F2 generation the seeds collected from the dwarf
recessive always produced dwarfs. On the other hand, the
seeds of the talls, though in physical appearance
indistinguishable, some bred tall and some produced both
tall and dwarfs in the usual proportion of 3 to1 (three of
the talls to one of the dwarfs), and the number of talls
that produced some dwarfs was 2 to1.
The significance of the above paragraphs is in the diversity
of characteristics, which follows the laws of transmission,
and appears before our eyes every day when observing the
progeny of our fowl, especially in characteristics such as
feather color, leg color, and comb types.
Mendel taught us that in each gamete there was either a
definite ability for the production of a recessive character
or a dominant character. He called them factors. These
factors, then, may be considered the unit characters which
appear in the development of the zygote.
Note of Interest: A unit character is a particular trait or
characteristic (usually controlled by a single gene or a set
of inseparable genes) that is passed on as a unit in
In the example that I have given you, tallness in the pea
would be considered a unit character, therefore the gametes
containing this unit character contain the factor for the
production of tallness.
In breeding for the proper comb: The breeder is constantly
battling in an effort to secure and fix the proper
characteristic and trait. With that said, let’s take a look
at the laws of inheritance, that determine which traits are
It has been proven that the rose-comb is dominant to the
straight (single) comb, such as possessed by the Single Comb
White Leghorn. It has also been proven that the pea-comb is
dominant to the straight (single) comb. Therefore, we see
two dominants in the rose and pea-combs.
Interestingly, when a rose-comb is crossed on a pea-comb a
new type is formed, that of the walnut-comb (so-called
because it resembles half of a walnut). The F2 generation,
that is, the progeny of the rose-comb and pea-comb crossed
on each other produced four types of combs, such as: 9
walnut, 3 rose, 3 pea, and 1 single.
If we study the above, we conclude that the walnut-comb
contains both dominant characters, the pea-comb and
rose-comb one dominant each, and the straight (single) comb
as a pure for both recessive characters.
The pea-comb and rose-comb factors are distinct and separate
entities, which, when combined, have an influence on each
other in the zygote, producing the walnut-comb, which is not
an intermediate between the two.
When one of these factors are alone in the zygote its
influence in the straight (single) comb factor is different;
that is, producing a pea-comb if a pea-comb factor, or a
rose-comb if a rose-comb factor.
The straight (single) comb is the form found in the Wild
Junglefowl, the Bankiva, which is said to be the ancestor of
all our domestic fowl. If this is true the reversion to the
straight (single) comb in the F2 generation is easily
explained. It is a reversion pure and simple, the recessive
factor coming to the surface.
You can learn a lot from breeding blues: It is difficult to
secure a slaty-blue color, with darker hackle and with dark
lacing of feathers on the breast. The off colors are white
splashed with black and pure blacks.
By studying the breeding of blues you will at all times
notice that they will always produce one black, one splashed
white, and two blues; the blues are heterozygous, and the
splashed whites and blacks are homozygous forms.
If the whites are bred together they will always produce
white offspring. Likewise, if the blacks are bred together
they will always produce black offspring, but if the blacks
and white are bred together they produce nothing but blues.
Specifically, the off colors breed twice as many blues as
when the blues are bred together. Therefore the blacks and
the whites are the pure breeds, while the blue is a mongrel
that can never be bred pure blue.
The distinction between a pure dominant and a heterozygote:
There are a few instances where a visible distinction can be
drawn between a pure dominant and a heterozygote. Certain
white breeds, as the White American Game, in which white
behaves as a dominant color; heterozygous whites, made by
crossing the dominant white birds with pure colored forms,
as the Black-Breasted Red American Game, or even the
Spangled American Game, almost invariably show ticks in
This shows the white dominance is not quite complete in the
American Game. It may be that the dominant white fowl may be
a colored bird plus a factor, which inhibits the development
of the color.
Note of interest: The Spangle in the American Game is a
genetic factor, and is carried in the sex chromosome of the
male. It follows the sex-linkage of inheritance.
Mendel's Theory Summarized: Mendel discovered an important
set of facts that are very important to us cockers and
backyard breeders, and that is the fact that:
• The germ-cells or gametes produced by cross-bred organisms
may be of the pure, paternal type, and incapable of
transmitting the opposite character.
• When such pure similar gametes of opposite sexes are
united in fertilization, the individuals so formed are free
from all flaws of the cross.
• There may be a perfect break between these germs in
respect of one of each pair of opposite characters.
The essential element of Mendel's discovery is the
segregation in the gametes of the factors corresponding to
the dominant and the recessive characters.
In the sperm-cell or egg-cell which it imparts it may give
off a gamete representing white plumage (W) or a gamete
representing black plumage (b), but not both at the same
time, that is, not a gamete representing half white and half
black. The gametes are distinct units. They are separated,
one from the other.
What is true of color applies in the same way to the comb,
and also to other Mendelian characteristics.
What is important is the fact that these two "potential unit
characters" do segregate, and that the adult organism cannot
have both. "Intermediate forms or blends do not occur in
“I am patient with stupidity but not with those who are proud of it.”