Milonix420
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Genotype and Phenotype Ratios
It must be remembered, in attempting to fix favorable
characteristics, that a monohybrid cross gives rise to four
possible recombinant genotypes, a dihybrid cross gives rise
to 16 possible recombinant genotypes, and so forth.
Phenotype and genotype ratios are probabilistic. If
recessive genes are desired for three traits it is not effective
to raise only 64 offspring and count on getting one homo-
zygous recessive individual. To increase the probability of
success it is better to raise hundreds of offspring, choosing
only the best homozygous recessive individuals as future
parents. All laws of inheritance are based on chance and
offspring may not approach predicted ratios until many
more have been phenotypically characterized and grouped
than the theoretical minimums.
The genotype of each individual is expressed by a
mosaic of thousands of subtle overlapping traits. It is the
sum total of these traits that determines the general pheno-
type of an individual. It is often difficult to determine if
the characteristic being selected is one trait or the blending
of several traits and whether these traits are controlled by
one or several pairs of genes. It often makes little difference
that a breeder does not have plants that are proven to breed
true. Breeding goals can still be established. The selfing of
F1 hybrids will often give rise to the variation needed in
the F2 generation for selecting parents for subsequent gen-
erations, even if the characteristics of the original parents
of the F1 hybrid are not known. It is in the following gen-
erations that fixed characteristics appear and the breeding
of pure strains can begin. By selecting and crossing individ-
uals that most nearly approach the ideal described by the
breeding goals, the variety can be continuously improved
even if the exact patterns of inheritance are never deter-
mined. Complementary traits are eventually combined into
one line whose seeds reproduce the favorable parental
traits. Inbreeding strains also allows weak recessive traits to
express themselves and these abnormalities must be dili-
gently removed from the breeding population. After five or
six generations, strains become amazingly uniform. Vigor is
occasionally restored by crossing with other lines or by
backcrossing.
Parental plants are selected which most nearly ap-
proach the ideal. If a desirable trait is not expressed by the
parent, it is much less likely to appear in the offspring. It is
imperative that desirable characteristics be hereditary and
not primarily the result of environment and cultivation.
Acquired traits are not hereditary and cannot be made
hereditary. Breeding for as few traits as possible at one
time greatly increases the chance of success. In addition to
the specific traits chosen as the aims of breeding, parents
are selected which possess other generally desirable traits
such as vigor and size. Determinations of dominance and
recessiveness can only be made by observing the outcome
of many crosses, although wild traits often tend to be
dominant. This is one of the keys to adaptive survival.
However, all the possible combinations will appear in the
F2 generation if it is large enough, regardless of dominance.
Now, after further simplifying this wonderful system
of inheritance, there are additional exceptions to the rules
which must be explored. In some cases, a pair of genes
may control a trait but a second or third pair of genes is
needed to express this trait. This is known as gene inter-
action. No particular genetic attribute in which we may be
interested is totally isolated from other genes and the ef-
fects of environment. Genes are occasionally transferred
in groups instead of assorting independently. This is known
as gene linkage, These genes are spaced along the same
chromosome and may or may not control the same trait.
The result of linkage might be that one trait cannot be in-
herited without another. At times, traits are associated with
the X and Y sex chromosomes and they may be limited to
expression in only one sex (sex linkage). Crossing over also
interferes with the analysis of crosses. Crossing over is the
exchanging of entire pieces of genetic material between two
chromosomes. This can result in two genes that are nor-
mally linked appearing on separate chromosomes where
they will be independently inherited. All of these processes
can cause crosses to deviate from the expected Mendelian
outcome. Chance is a major factor in breeding Cannabis, or
any introduced plant, and the more crosses a breeder
attempts the higher are the chances of success.
Variate, isolate, intermate, evaluate, multiplicate, and
disseminate are the key words in plant improvement. A
plant breeder begins by producing or collecting various
prospective parents from which the most desirable ones
are selected and isolated. Intermating of the select parents
results in offspring which must be evaluated for favorable
characteristics. If evaluation indicates that the offspring are
not improved, then the process is repeated. Improved off-
spring are multiplied and disseminated for commercial use.
Further evaluation in the field is necessary to check for
uniformity and to choose parents for further intermating.
This cyclic approach provides a balanced system of plant
improvement.
It must be remembered, in attempting to fix favorable
characteristics, that a monohybrid cross gives rise to four
possible recombinant genotypes, a dihybrid cross gives rise
to 16 possible recombinant genotypes, and so forth.
Phenotype and genotype ratios are probabilistic. If
recessive genes are desired for three traits it is not effective
to raise only 64 offspring and count on getting one homo-
zygous recessive individual. To increase the probability of
success it is better to raise hundreds of offspring, choosing
only the best homozygous recessive individuals as future
parents. All laws of inheritance are based on chance and
offspring may not approach predicted ratios until many
more have been phenotypically characterized and grouped
than the theoretical minimums.
The genotype of each individual is expressed by a
mosaic of thousands of subtle overlapping traits. It is the
sum total of these traits that determines the general pheno-
type of an individual. It is often difficult to determine if
the characteristic being selected is one trait or the blending
of several traits and whether these traits are controlled by
one or several pairs of genes. It often makes little difference
that a breeder does not have plants that are proven to breed
true. Breeding goals can still be established. The selfing of
F1 hybrids will often give rise to the variation needed in
the F2 generation for selecting parents for subsequent gen-
erations, even if the characteristics of the original parents
of the F1 hybrid are not known. It is in the following gen-
erations that fixed characteristics appear and the breeding
of pure strains can begin. By selecting and crossing individ-
uals that most nearly approach the ideal described by the
breeding goals, the variety can be continuously improved
even if the exact patterns of inheritance are never deter-
mined. Complementary traits are eventually combined into
one line whose seeds reproduce the favorable parental
traits. Inbreeding strains also allows weak recessive traits to
express themselves and these abnormalities must be dili-
gently removed from the breeding population. After five or
six generations, strains become amazingly uniform. Vigor is
occasionally restored by crossing with other lines or by
backcrossing.
Parental plants are selected which most nearly ap-
proach the ideal. If a desirable trait is not expressed by the
parent, it is much less likely to appear in the offspring. It is
imperative that desirable characteristics be hereditary and
not primarily the result of environment and cultivation.
Acquired traits are not hereditary and cannot be made
hereditary. Breeding for as few traits as possible at one
time greatly increases the chance of success. In addition to
the specific traits chosen as the aims of breeding, parents
are selected which possess other generally desirable traits
such as vigor and size. Determinations of dominance and
recessiveness can only be made by observing the outcome
of many crosses, although wild traits often tend to be
dominant. This is one of the keys to adaptive survival.
However, all the possible combinations will appear in the
F2 generation if it is large enough, regardless of dominance.
Now, after further simplifying this wonderful system
of inheritance, there are additional exceptions to the rules
which must be explored. In some cases, a pair of genes
may control a trait but a second or third pair of genes is
needed to express this trait. This is known as gene inter-
action. No particular genetic attribute in which we may be
interested is totally isolated from other genes and the ef-
fects of environment. Genes are occasionally transferred
in groups instead of assorting independently. This is known
as gene linkage, These genes are spaced along the same
chromosome and may or may not control the same trait.
The result of linkage might be that one trait cannot be in-
herited without another. At times, traits are associated with
the X and Y sex chromosomes and they may be limited to
expression in only one sex (sex linkage). Crossing over also
interferes with the analysis of crosses. Crossing over is the
exchanging of entire pieces of genetic material between two
chromosomes. This can result in two genes that are nor-
mally linked appearing on separate chromosomes where
they will be independently inherited. All of these processes
can cause crosses to deviate from the expected Mendelian
outcome. Chance is a major factor in breeding Cannabis, or
any introduced plant, and the more crosses a breeder
attempts the higher are the chances of success.
Variate, isolate, intermate, evaluate, multiplicate, and
disseminate are the key words in plant improvement. A
plant breeder begins by producing or collecting various
prospective parents from which the most desirable ones
are selected and isolated. Intermating of the select parents
results in offspring which must be evaluated for favorable
characteristics. If evaluation indicates that the offspring are
not improved, then the process is repeated. Improved off-
spring are multiplied and disseminated for commercial use.
Further evaluation in the field is necessary to check for
uniformity and to choose parents for further intermating.
This cyclic approach provides a balanced system of plant
improvement.