Download Horse Genetics

Horse Genetics
Nature ordained that _____________ be applied to horse
breeding long before there were geneticists. Prior to the
domestication of horses, there was __________ _______
for speed and stamina. One of the most important defense
mechanisms of the horse was to outrun its enemies.
 Natural selection was probably very effective in improving
speed and endurance, since the slower horses were
eliminated by predators.
Horse Genetics
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Many horse _______ have been _________ genetics as
they concern themselves with the are of ________. Their
guiding concept of heredity is that “like begets like”.
Breeders in the 18th century made a tremendous
contribution pointing the way toward horse ________
before Mendel’s _______ became known to the world.
As knowledge of genetics developed, there ________ an
understanding of the science that underlies the art of horse
breeding.
Horse Genetics
Genetics
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The _________ of animals are made up of millions or even
billions of _________ cells.
Each cell contains a __________ in which there are a
number of pairs of bundles called _____________.
In turn, the chromosomes carry ________ of minute
particles called ________, which are the basic hereditary
material.
The nucleus of each cell of a horse contains
____ pairs of chromosomes, or a total of _____.
Horse Genetics
Genetics
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There are _______ of pairs of genes on each chromosome.
Genes determine all the ________ characteristics of
animals from the _____ type to the _____ of the hair.
The mule has an ______ number of chromosomes and
cannot __________.
The ________ of an animal refers to the specific genes it
possesses on its chromosomes.
__________ describes the complete set of “instructions”
for making an organism.
Horse Genetics
Genetics
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__________ gene expression has a full allele effect. An
example would be when a gray horse produces a gray
horse.
___________ character appears only when both members
of a pair of alleles are alike.
The job of __________ qualities from one _________ to
the next is performed by the gene cells- a _______ from
the male and an ______, or ______ from the female.
Horse Genetics
Genetics
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There are alternate forms of each gene. The _______ gene
forms are referred to as alleles. If the alleles are the same,
the condition is referred to as ___________. If the alleles
are different, the condition is called ___________.
_________ and ____________ are the tools through which
the horse breeder may obtain stallions and mares whose
chromosomes and genes contain ____________ hereditary
determiners-animals that are genetically more
homozygous.
Horse Genetics
Genetics
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Gene changes are known as ________. A mutation may
be defined as a _________ variation that is later passed on
through ____________ and that results from changes in a
gene or genes.
Horse Genetics
Simple Gene Inheritance (Qualitative Traits)
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In the simplest type of inheritance only _____ pair of genes
is involved. Thus, a _______ of genes may be ________
for the color of body hair in horses.
The idea that certain basic colors may have a rather ______
explanation of inheritance should not alter the fact that
other genes may play an important role through their
___________ on basic schemes.
The possible gene ____________ are governed by the laws
of chance.
Horse Genetics
Simple Gene Inheritance (___________________)
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Other possible examples of _________ gene inheritance in
horses might include _____ color and the set of the ears on
the head.
Horse Genetics
Dominant and Recessive Alleles
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A dominant ___________ may cover up a recessive allele.
Therefore, a horse’s breeding ____________ cannot be
recognized by its _______________ (how it looks).
____________ genes can be passed on from generation to
generation, _____________ only when ______ animals,
both of which carry the same recessive allele, happen to
mate.
Horse Genetics
Dominant and Recessive Alleles
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Reputable breeders have an obligation, not only to
themselves, but to their customers. Purebred animals
must be __________ of _________ genes by
___________ those stallions and mares that are known to
have transmitted the undesirable recessive gene.
Horse Genetics
Incomplete Dominance
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In some cases, dominance is neither __________ nor
_____________, but __________ or ___________ and
expresses in a variety of ways.
Perhaps the best known case of this type in horses is the
____________ color. Genetic studies of the Palomino
indicate that the color is probably ___________- that it
cannot be made _______ breeding, no matter how long or
how persistent the effort.
Horse Genetics
Multiple Gene Inheritance (Quantitative Traits)
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Important characters such as speed are due to many genes;
thus, they are called _________-__________ characters.
_____________ inheritance refers to the ________ to
which a characteristic is __________.
For example, all Thoroughbred horses can run and all
inherit some ability to run, but it is the degree to which
they inherit the ability that is important.
In quantitative inheritance, the extremes (either good or
bad) tend to swing back to the average.
Horse Genetics
Horse Color
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Recent advances in ________ have allowed us to
understand better how coat color is inherited, thus making
it possible to plan __________ that will produce foals of a
certain color.
Horse Genetics
Gene _______
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Genetic __________ of black color restricted to the points
of a horse is through gene A, or the A allele.
The ______ allele is _________.
A uniformly black horse has the ________ genotype ____.
Horse Genetics
Gene ___
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Gene E, or the E allele, ________ the expression of black
hair on the body.
The _________ form _____, results in uniformly redcolored horses.
The ____ gene is related to (and can mask) the A gene.
Horse Genetics
Gene ____
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________ coloring is due to the dominant gene _____.
Any horses with the _____ allele will be ______; ___________ horses will have the genotype _______.
Gray horses can be born ______ color.
Horse Genetics
Gene _______
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Solid ________ coloring is controlled by gene _____.
The __________ homozygous (______) condition is
________; thus, all white horses have the genotype.
All non-white horses have the genotype ______.
Horse Genetics
Gene ______ and _______
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The ___ and ____ alleles are _______ alleles. Gene C affects only
______ pigment and causes the pigment to lighten.
The C gene does not affect ________ pigment.
Gene D _________ from gene C in that it can dilute both _______
and __________ pigment.
With the D allele, _______ is diluted to a _______ or _________,
and _________ is diluted to a yellow-tan.
Horses with the D allele also show ________ marks such as the
dorsal stripe, shoulder stripes, and leg barring.
Horse Genetics
Gene _____
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The spotting of paint and pinto horses is controlled by the
___________ gene TO.
The tobiano color pattern is _________; thus, __________
must have the genotype ________.
Homozygous TOTO horses are _______ and are sought
after by horse breeders for their ability to always produce
_________foals.
Genetic tests are available to determine whether a horse is
homozygous.
Horse Genetics
Heritability of Performance Traits
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Relatively little scientific work has been done on the
heritability of ___________ of horses- on the genetics of
________ ability, _________ ability, ________ ability, etc.
The horse is the ______ farm animal to which the science
of genetics has been added to the ______ of breeding.
Differences in the performance ability (working, racing,
jumping) are due to _______ major forces - _________
and _________.
Horse Genetics
Heritability of Performance Traits
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The important __________ factors in determining the
_________ performance of horses are _________ (both
prenatal and postnatal), _____ care, quality of ________,
_______ of the handler, and _________.
An important genetic ___________ is that traits as such
are not inherited. The ability to respond to a _______ set of
environmental conditions in order to produce a trait with a
measurable effect is inherited.
_________ estimates on the heritability of performance
traits in horses are limited in comparison with those for
other species.
Horse Genetics
The following conditions would tend to indicate a
_____________ defect in horses:
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If the defect had previously been reported as hereditary in
the same breed.
If it occurred more frequently within certain families or
when there had been inbreeding.
If it occurred in more than one season and when different
rations had been fed.
Horse Genetics
The following __________ might be accepted as indications
that the abnormality was due to a ___________deficiency:
 If it had previously been reliably reported to be due to a
nutritional deficiency.
 If it appeared to be restricted to a certain area.
 If it occurred when the ration of the dam was known to be
deficient.
 If it disappeared when an improved ration was fed.