The Appaloosa is an American horse breed best known for its colorful spotted coat pattern. There is a wide range of body types within the breed, stemming from the influence of multiple breeds of horses throughout its history; each horse's color pattern is genetically the result of various spotting patterns overlaid on top of one of several recognized base coat colors. The color pattern of the Appaloosa is of interest to those who study equine coat color genetics, as it and several other physical characteristics are linked to the leopard complex mutation. Appaloosas are prone to congenital stationary night blindness. Artwork depicting prehistoric horses with leopard spotting exists in prehistoric cave paintings in Europe. Images of domesticated horses with leopard spotting patterns appeared in artwork from Ancient Greece and Han dynasty China through the early modern period. In North America, the Nez Perce people of what today is the United States Pacific Northwest developed the original American breed.
Settlers once referred to these spotted horses as the "Palouse horse" after the Palouse River, which ran through the heart of Nez Perce country. The name evolved into "Appaloosa"; the Nez Perce lost most of their horses after the Nez Perce War in 1877, the breed fell into decline for several decades. A small number of dedicated breeders preserved the Appaloosa as a distinct breed until the Appaloosa Horse Club was formed as the breed registry in 1938; the modern breed maintains bloodlines tracing to the foundation bloodstock of the registry. Today, the Appaloosa is one of the most popular breeds in the United States, it is best known as a stock horse used in a number of western riding disciplines, but is a versatile breed with representatives seen in many other types of equestrian activity. Appaloosas have been used in many movies. Appaloosa bloodlines have influenced other horse breeds, including the Pony of the Americas, the Nez Perce Horse, several gaited horse breeds; the Appaloosa is best known for its distinctive, leopard complex-spotted coat, preferred in the breed.
Spotting occurs in several overlay patterns on one of several recognized base coat colors. There are three other distinctive, "core" characteristics: mottled skin, striped hooves, eyes with a white sclera. Skin mottling is seen around the muzzle, eyes and genitalia. Striped hooves are a common trait, quite noticeable on Appaloosas, but not unique to the breed; the sclera is the part of the eye surrounding the iris. Because the occasional individual is born with little or no visible spotting pattern, the ApHC allows "regular" registration of horses with mottled skin plus at least one of the other core characteristics. Horses with two ApHC parents but no "identifiable Appaloosa characteristics" are registered as "non-characteristic," a limited special registration status. There is a wide range of body types in the Appaloosa, in part because the leopard complex characteristics are its primary identifying factors, because several different horse breeds influenced its development; the weight range varies from 950 to 1,250 pounds, heights from 14 to 16 hands.
However, the ApHC does not allow draft breeding. The original "old time" or "old type" Appaloosa was a narrow-bodied, rangy horse; the body style reflected a mix that started with the traditional Spanish horses common on the plains of America before 1700. 18th-century European bloodlines were added those of the "pied" horses popular in that period and shipped en masse to the Americas once the color had become unfashionable in Europe. These horses were similar to a tall, slim Thoroughbred-Andalusian type of horse popular in Bourbon-era Spain; the original Appaloosa tended to have a convex facial profile that resembled that of the warmblood-Jennet crosses first developed in the 16th century during the reign of Charles V. The old-type Appaloosa was modified by the addition of draft horse blood after the 1877 defeat of the Nez Perce, when U. S. Government policy forced the Indians to become farmers and provided them with draft horse mares to breed to existing stallions; the original Appaloosas had a sparse mane and tail, but, not a primary characteristic, as many early Appaloosas did have full manes and tails.
There is a possible genetic link between the leopard complex and sparse mane and tail growth, although the precise relationship is unknown. After the formation of the Appaloosa Horse Club in 1938, a more modern type of horse was developed after the addition of American Quarter Horse and Arabian bloodlines; the addition of Quarter Horse lines produced Appaloosas that performed better in sprint racing and in halter competition. Many cutting and reining horses resulted from old-type Appaloosas crossed on Arabian bloodlines via the Appaloosa foundation stallion Red Eagle. An infusion of Thoroughbred blood was added during the 1970s to produce horses more suited for racing. Many current breeders attempt to breed away from the sparse, "rat tail" trait, therefore modern Appaloosas have fuller manes and tails; the coat color of an Appaloosa is a combination of a base color with an overlaid spotting pattern. The base colors r
Tennessee Walking Horse
The Tennessee Walking Horse or Tennessee Walker is a breed of gaited horse known for its unique four-beat running-walk and flashy movement. It was developed in the southern United States for use on farms and plantations, it is a popular riding horse due to smooth gaits and sure-footedness. The Tennessee Walking Horse is seen in the show ring, but is popular as a pleasure and trail riding horse using both English and Western equipment. Tennessee Walkers are seen in movies, television shows and other performances; the breed was developed beginning in the late 18th century when Narragansett Pacers and Canadian Pacers from the eastern United States were crossed with gaited Spanish Mustangs from Texas. Other breeds were added, in 1886 a foal named Black Allan was born, he is now considered the foundation sire of the breed. In 1935 the Tennessee Walking Horse Breeders' Association was formed, it closed the studbook in 1947. In 1939, the first Tennessee Walking Horse National Celebration was held. In the early 21st century, this annual event has attracted considerable attention and controversy, because of efforts to prevent abuse of horses, practiced to enhance their performance in the show ring.
The two basic categories of Tennessee Walking Horse show competition are called "flat-shod" and "performance", distinguished by desired leg action. Flat-shod horses, wearing regular horseshoes, exhibit less exaggerated movement. Performance horses are shod with built-up pads or "stacks", along with other weighted action devices, creating the so-called "Big Lick" style; the United States Equestrian Federation and some breed organizations now prohibit the use of stacks and action devices at shows they sanction. In addition, the Tennessee Walking Horse is the breed most affected by the Horse Protection Act of 1970, it prohibits the practice of soring, abusive practices which were used to enhance the Big Lick movement prized in the show ring. Despite the law, some horses are still being abused; the controversy over continuing soring practices has led to a split within the breed community, criminal charges against a number of individuals, the creation of several separate breed organizations. The modern Tennessee Walking Horse is described as "refined and elegant, yet solidly built".
It is a tall horse with a long neck. The head is well-defined, with well-placed ears; the breed averages 14.3 to 17 hands high and 900 to 1,200 pounds. The shoulders and hip are sloping, with a short back and strong coupling; the hindquarters are of "moderate thickness and depth", well-muscled, it is acceptable for the hind legs to be over-angulated, cow-hocked or sickle-hocked. They are found in all solid colors, several pinto patterns. Common colors such as bay and chestnut are found, as are colors caused by dilution genes such as the dun, champagne and silver dapple genes. Pinto patterns include overo and tobiano; the Tennessee Walking Horse has a reputation for having a calm disposition and a smooth riding gait. While the horses are famous for flashy movement, they are popular for trail and pleasure riding as well as show; the Tennessee Walking Horse is best known for its running-walk. This is a four-beat gait with the same footfall pattern as a regular, or flat, but faster. While a horse performing a flat walk moves at 4 to 8 miles per hour, the running walk allows the same horse to travel at 10 to 20 miles per hour.
In the running walk, the horse's rear feet overstep the prints of its front feet by 6 to 18 inches, with a longer overstep being more prized in the Tennessee Walking Horse breed. While performing the running walk, the horse nods its head in rhythm with its gait. Besides the flat and running walks, the third main gait performed by Tennessee Walking Horses is the canter; some members of the breed perform other variations of lateral ambling gaits, including the rack, stepping pace, fox trot and single-foot, which are allowable for pleasure riding but penalized in the show ring. A few Tennessee Walking Horses can trot, have a long, reaching stride; the Tennessee Walker originated from the cross of Narragansett Pacer and Canadian Pacer horses brought to Kentucky starting in 1790, with gaited Spanish Mustangs imported from Texas. These horses were bred on the limestone pastures of Middle Tennessee, became known as "Tennessee Pacers". Used as all-purpose horses on plantations and farms, they were used for riding and racing.
They were known for their smooth sure-footedness on the rocky Tennessee terrain. Morgan, Standardbred and American Saddlebred blood was added to the breed through decades of breeding. In 1886, Black Allan was born. By the stallion Allendorf and out of a Morgan mare named Maggie Marshall, he became the foundation sire of the Tennessee Walking Horse breed. A failure as a trotting horse, due to his insistence on pacing, Black Allan was instead used for breeding. From his line, a foal named Roan Allen was born in 1904. Able to perform several ambling gaits, Roan Allen became a successful show horse, in turn sired several famous Tennessee Walking Horses; the Tennessee Walking Horse Breeders' Association was formed in 1935. To reflect interest in showing horses, the name was changed in 1974 to the current Tennessee Walking Horse Breeders' and Exhibitors' Association; the stud book was closed in 1947, meaning that since that date every Tennessee Walker must have both its dam and stud registered in order to be eligible for registration.
In 1950, the United States Department of
The dun gene is a dilution gene that affects both red and black pigments in the coat color of a horse. The dun gene has the ability to affect the appearance of all black, bay, or chestnut-based horses by lightening the base body coat and suppressing the underlying base color to the mane, tail and primitive markings; the classic dun is a gray-gold or tan, characterized by a body color ranging from sandy yellow to reddish brown. A dun horse always has a dark stripe down the middle of its back, a tail and mane darker than the body coat, darker face and legs. Other duns may appear a light yellowish shade, or a steel gray, depending on the underlying coat color genetics. Manes, primitive markings, other dark areas are the shade of the undiluted base coat color; the dun allele is a simple dominant, so the phenotype of a horse with either one copy or two copies of the gene is dun. It has a stronger effect than other dilution genes, such as the silver dapple gene, which acts only on black-based coats, or the cream gene, an incomplete dominant which must be homozygous to be expressed, when heterozygous is only visible on bay and chestnut coats, to a lesser degree.
The dun gene is characterized by primitive markings, which are darker than the body color. Primitive markings include: Dorsal stripe, seen universally on all duns Horizontal striping on the back of forelegs, common on most duns, although at times, rather faint Shoulder blade stripe, the least seen of the primitive markingsDorsal striping does not guarantee the horse carries the dun gene. A countershading gene can produce faint dorsal striping in breeds such as the Arabian horse or the Thoroughbred, where the dun gene is not known to be carried in the gene pool. A primary characteristic of the dun gene is the dorsal stripe, most duns have visual leg striping; the shoulder stripes are less common and fainter, but visible on horses with a short summer coat. The dun coat color is thought to be a primitive trait in the horse; this is because equines appearing in prehistoric cave paintings are dun, because several related species in the genus Equus are known to have been dun. These species include both subspecies of Equus ferus, the extinct Equus lambei, the extant onager and kiang.
The dun gene has a stronger dilution effect on the body than the mane, tail and primitive markings, so lightens the body coat more. This explains why points on a dun are a shade darker than the coat, or in the case of a "classic" dun, the mane and legs are black or only diluted. Dun called bay dun, classic dun or zebra dun, the most common type of dun, has a tan or gold body with black mane and primitive markings. Genetically, the horse has an underlying bay coat color, acted upon by the dun gene. Red dun called claybank or fox dun, horses do not have black points, as there is no black on the horse to be affected. Instead, the points and primitive markings are a darker shade of red than the coat. Genetically, the horse has an underlying chestnut coat color, acted upon by the dun gene. Grullo or grulla called blue dun or "mouse" dun, is a smoky, bluish, to mouse-brown color and can vary from light to dark, they have black points and they have a dark or black head, an identifying characteristic of this color.
The primitive markings are all black. Genetically, the horse has an underlying black coat color, acted upon by the dun gene. Unlike a blue roan, there are no intermingled black and white hairs, unlike a true gray, which intermingles light and dark hairs, the color does not change to a lighter shade as the horse ages. With a dun, the hair color itself is one solid shade. Since the dun gene, when on a "bay dun" horse, can resemble buckskin, in that both colors feature a light-colored coat with a dark mane and tail, classic duns are confused with buckskins; the difference between these two colors is the dun as a tan color, somewhat duller than the more cream or gold buckskin, duns possess primitive markings. Some buckskins do show countershading, but it is not related to the primitive markings of dun factor horses. Genetically, a bay dun is a bay horse with the dun gene that causes the lighter coat color and the primitive markings. A buckskin is bay horse with the addition of the cream gene, causing the coat color to be diluted from red to gold without primitive markings.
A red dun may be confused with a perlino, genetically a bay horse with two copies of the cream gene, which creates a horse with a cream-colored body but a reddish mane and tail. However, perlinos are lighter than a red dun and have blue eyes. To further confuse matters, it is possible for a horse to carry both cream dilution genes. In the Fjord horse, duns that carry the creme dilution are called uls dun or white dun and yellow dun by their respective coat colors. On such horses, the light-shaded primitive markings are most noticeable during the summer months, when the winter hair sheds. Countershading is a a darker shade of the body color rather than the near-black of primitive markings on bay duns, but it may be harder to differentiate between countershading and a dorsal stripe on light-colored horses such as red duns. In such cases, pedigree analysis, DNA testing, studying possible offspring, the presence of other primitive markings are used to determine whether a horse is a dun. Genetic analysi
Xena: Warrior Princess
Xena: Warrior Princess is an American fantasy television series filmed on location in New Zealand. The series aired in first-run syndication from September 4, 1995 to June 18, 2001. Critics have praised the series for its strong female protagonist, it has acquired a strong cult following, attention in fandom and academia, has influenced the direction of other television series. Writer-director-producer Robert Tapert created the series in 1995 under his production tag, Renaissance Pictures, with executive producers R. J. Stewart and Sam Raimi; the series narrative follows Xena, an infamous warrior on a quest to seek redemption for her past sins against the innocent by using her formidable fighting skills to now help those who are unable to defend themselves. Xena is accompanied by Gabrielle, who during the series changes from a simple farm-girl into an Amazon warrior and Xena's comrade-in-arms. In 2012 star Lucy Lawless confirmed; the show is a spin-off of the television series Hercules: The Legendary Journeys.
Aware that the character of Xena had become successful among the public, the producers of the series decided to launch a spin-off series based on her adventures. Xena became a successful show which has aired in more than 108 countries around the world since 1998. In 2004 and 2007, it ranked #9 and #10 on TV Guide's Top Cult Shows Ever and the title character ranked #100 on Bravo's 100 Greatest TV Characters. Xena's success has led to hundreds of tie-in products, including comics, video games and conventions, realized annually since 1998 in Pasadena, California and in London; the series soared past its predecessor in popularity. In its second season it became the top-rated syndicated drama series on American television. For all six years, Xena remained in the top five. Cancellation of the series was announced in October 2000, the series finale aired in the summer of 2001. On August 13, 2015 NBC Entertainment chairman Bob Greenblatt said a Xena reboot was in development, with Raimi and Tapert returning as executive producers, with the show's debut sometime in 2016.
Javier Grillo-Marxuach was hired as writer and producer for the reboot, but left the project in April 2017 because of creative differences. In August 2017, NBC announced that it had cancelled its plans for the reboot for the foreseeable future. Xena: Warrior Princess is set in a fantasy version of ancient Greece and was filmed in New Zealand; some filming locations are confidential, but many scenes were recorded in places such as the Waitakere Ranges Regional Park, part of the Auckland Regional parks credited at the end of the episodes. The Ancient Greece depicted in the show is derived from historical locations and customs, modifying known places and events – battles, trading routes, so on – to generate an attractive fictional world; the settlements are presented as a mixture of walled villages and rural hamlets set in a lush green, mountainous landscape. They are seen under attack from warlords, travelling between them involves frequent encounters with small bands of outlaws. All of the main towns are named after historic towns of Ancient Greece, exhibit some of their essential characteristics – Amphipolis, Athens, Corinth and Cirra, burnt to the ground by Xena's army.
As the show progressed, events took place throughout more modern times and places, from Cleopatra's Alexandria to Julius Caesar's Rome. The mythology of the show transitioned from that of the Olympian Gods to include Judeo-Christian elements. Eastern religions were touched on as well, with little regard to accurate time-and-place concerns. One episode, "The Way", which loosely interpreted elements of Hinduism as major plot points, generated controversy, requiring the producers to add a disclaimer at the head of the episode and a tag explaining the episode's intentions at its end. Mythological and supernatural locations are presented as real, physical places accessed through physical portals hidden in the landscape such as lakes and caves, they include the Elysian Fields, the River Styx, Valhalla and Hell. The inhabitants of such places – gods, mythological beings and forces – are for the most part manifested as human characters who can move at will between their domains and the real world. Ares, the Greek God of War, for instance, is an egotistical man who wears studded black leather, Aphrodite, Goddess of Love, is a California valley girl who uses typical valley girl slang and dresses in flowing, translucent pink gowns.
Xena is a historical fantasy set in ancient Greece, although the setting is flexible in both time and location and features Egyptian, Chinese, Central Asian, Medieval European elements. The flexible fantasy framework of the show accommodates a considerable range of theatrical styles, from high melodrama to slapstick comedy, from whimsical and musical to all-out action and adventure. While the show is set in ancient times, its themes are modern and it investigates the ideas of taking responsibility for past misdeeds, the value of human life, personal liberty and sacrifice, friendship; the show addresses ethical dilemmas, such as the morality of pacifism.
The Haflinger known as the Avelignese, is a breed of horse developed in Austria and northern Italy during the late nineteenth century. Haflinger horses are small, are always chestnut with flaxen mane and tail, have distinctive gaits described as energetic but smooth, are well-muscled yet elegant; the breed traces its ancestry to the Middle Ages. Haflingers, developed for use in mountainous terrain, are known for their hardiness, their current conformation and appearance are the result of infusions of bloodlines from Arabian and various European breeds into the original native Tyrolean ponies. The foundation sire, 249 Folie, was born in 1874. All Haflingers can trace their lineage back to Folie through one of seven bloodlines. World Wars I and II, as well as the Great Depression, had a detrimental effect on the breed, lower-quality animals were used at times to save the breed from extinction. During World War II, breeders focused on horses that were shorter and more draft-like, favored by the military for use as packhorses.
The emphasis after the war shifted toward animals of increased height. In the postwar era, the Haflinger was indiscriminately crossed with other breeds and some observers feared the breed was in renewed danger of extinction. However, starting in 1946, breeders focused on producing purebred Haflingers and a closed stud book was created. Interest in the breed increased in other countries and between 1950 and 1974 the population grew while the overall European horse population decreased. Population numbers continued to increase and as of 2005 250,000 Haflingers existed worldwide. There are breeding farms in several countries, although most of the breeding stock still comes from Austria. In 2003, a Haflinger became the first horse to be cloned. Haflingers have many uses including light draft, harness work and various under-saddle disciplines such as endurance riding, equestrian vaulting and therapeutic riding, they are still used by the Austrian and German armies for work in rough terrain. The World Haflinger Federation, the international governing body that controls breed standards for the Haflinger, is made up of a confederation of 22 national registries, helps set breeding objectives and rules for its member organizations.
The name "Haflinger" comes from the village of Hafling. The breed is called the Avelignese, from the Italian name for Hafling, Avelengo or Aveligna. Haflingers are always chestnut in color and come in shades ranging from a light gold to a rich golden chestnut or liver hue; the mane and tail are flaxen. The height of the breed has increased since the end of World War II, when it stood an average of 13.3 hands. The desired height today is between 15 hands. Breeders are discouraged from breeding horses under the minimum size, but taller individuals may pass inspection if they otherwise meet requirements of the breed registry; the breed has a refined light poll. The neck is of medium length, the withers are pronounced, the chest deep; the back is medium-long and muscular, the croup is long sloping and well-muscled. The legs are clean, with broad, flat knees and powerful hocks showing clear definition of tendons and ligaments; the Haflinger has ground-covering gaits. The walk is energetic; the trot and canter are elastic and athletic with a natural tendency to be light on the forehand and balanced.
There is some knee action, the canter has a distinct motion forwards and upwards. One important consideration in breeding during the second half of the 20th century was temperament. A requirement for a quiet, kind nature has become part of official breed standards and is checked during official inspections; some sources recognize two types of Haflinger, a shorter, heavier type used for draft work and a taller, lighter type used for pleasure riding, light driving and under-saddle competition. The Food and Agriculture Organization recognizes both an "Avelignese" and an "Avelignese Tradizionale" as existing in Italy, although, as of 2007, only 13 of the latter existed, including only one breeding stallion. However, all breed organizations register only one type. All Haflingers today trace their lineage through one of seven stallion lines to Folie, the foundation stallion of the breed. Colts are given a name beginning with the letter or letters denoting their stallion line, fillies are given a name beginning with the first letter of their dam's name.
The exceptions are France, where foals are given a name beginning with a letter of the alphabet designated to be used for that year. The seven stallion lines are: A-line. Founded by Anselmo, born 1926. One of the most prevalent lines today, descendants include the second-largest number of stallions at stud. Anselmo was brought back to stud at the age of 21, when a lack of stallions after World War II led to concerns that the line would not survive, produced several stallions now represented in all Haflinger breeding populations worldwide. B-line. Founded by Bolzano, born 1915. Bolzano's less common line, although strong in Austria, is not prevalent elsewhere; the line is spreading nevertheless. S. and several European countries including Great Britain are establishing Bolzano lines. M-line. Founded by Massimo, born 1927. An Italian
Zygosity is the degree of similarity of the alleles for a trait in an organism. Most eukaryotes have two matching sets of chromosomes. Diploid organisms have the same loci on each of their two sets of homologous chromosomes except that the sequences at these loci may differ between the two chromosomes in a matching pair and that a few chromosomes may be mismatched as part of a chromosomal sex-determination system. If both alleles of a diploid organism are the same, the organism is homozygous at that locus. If they are different, the organism is heterozygous at that locus. If one allele is missing, it is hemizygous; the DNA sequence of a gene varies from one individual to another. Those variations are called alleles. While some genes have only one allele because there is low variation, others have only one allele because deviation from that allele can be harmful or fatal, but most genes have two or more alleles. The frequency of different alleles varies throughout the population; some genes may have two alleles with equal distribution.
For other genes, one allele may be common, another allele may be rare. Sometimes, one allele is a disease-causing variation. Sometimes, the different variations in the alleles make no difference at all in the function of the organism. In diploid organisms, one allele is inherited from one from the female parent. Zygosity is a description of whether those two alleles have different DNA sequences. In some cases the term "zygosity" is used in the context of a single chromosome; the words homozygous and hemizygous are used to describe the genotype of a diploid organism at a single locus on the DNA. Homozygous describes a genotype consisting of two identical alleles at a given locus, heterozygous describes a genotype consisting of two different alleles at a locus, hemizygous describes a genotype consisting of only a single copy of a particular gene in an otherwise diploid organism, nullizygous refers to an otherwise-diploid organism in which both copies of the gene are missing. A cell is said to be homozygous for a particular gene when identical alleles of the gene are present on both homologous chromosomes.
The cell or organism in question is called a homozygote. True breeding organisms are always homozygous for the traits. An individual, homozygous-dominant for a particular trait carries two copies of the allele that codes for the dominant trait; this allele called the "dominant allele", is represented by a capital letter. When an organism is homozygous-dominant for a particular trait, the genotype is represented by a doubling of the symbol for that trait, such as "PP". An individual, homozygous-recessive for a particular trait carries two copies of the allele that codes for the recessive trait; this allele called the "recessive allele", is represented by the lowercase form of the letter used for the corresponding dominant trait. The genotype of an organism, homozygous-recessive for a particular trait is represented by a doubling of the appropriate letter, such as "pp". A diploid organism is heterozygous at a gene locus when its cells contain two different alleles of a gene; the cell or organism is called a heterozygote for the allele in question, therefore, heterozygosity refers to a specific genotype.
Heterozygous genotypes are represented by a capital letter and a lowercase letter, such as "Rr" or "Ss". Alternatively, a heterozygote for gene "R" is assumed to be "Rr"; the capital letter is written first. If the trait in question is determined by simple dominance, a heterozygote will express only the trait coded by the dominant allele, the trait coded by the recessive allele will not be present. In more complex dominance schemes the results of heterozygosity can be more complex. A heterozygous genotype can have a higher relative fitness than either the homozygous dominant or homozygous recessive genotype - this is called a heterozygote advantage. A chromosome in a diploid organism is hemizygous; the cell or organism is called a hemizygote. Hemizygosity is observed when one copy of a gene is deleted, or, in the heterogametic sex, when a gene is located on a sex chromosome. Hemizygosity must not be confused with haploinsufficiency, which describes a mechanism for producing a phenotype. For organisms in which the male is heterogametic, such as humans all X-linked genes are hemizygous in males with normal chromosomes, because they have only one X chromosome and few of the same genes are on the Y chromosome.
Transgenic mice generated through exogenous DNA microinjection of an embryo's pronucleus are considered to be hemizygous, because the introduced allele is expected to be incorporated into only one copy of any locus. A transgenic individual can be bred to homozygosity and maintained as an inbred line to reduce the need to confirm the genotype of each individual. In cultured mammalian cells, such as the Chinese hamster ovary cell line, a number of genetic loci are present in a functional hemizygous state, due to mutations or deletions in the other alleles. A nullizygous organism carries two mutant alleles for the same gene; the mutant alleles are both complete loss-of-function or'null' alleles, so homozygous null and n
Equestrianism, more known as horse riding or horseback riding, refers to the skill and sport of riding, steeplechasing or vaulting with horses. This broad description includes the use of horses for practical working purposes, recreational activities, artistic or cultural exercises, competitive sport. Horses are trained and ridden for practical working purposes, such as in police work or for controlling herd animals on a ranch, they are used in competitive sports including, but not limited to, endurance riding, reining, show jumping, tent pegging, polo, horse racing and rodeo. Some popular forms of competition are grouped together at horse shows where horses perform in a wide variety of disciplines. Horses are used for non-competitive recreational riding such as fox hunting, trail riding, or hacking. There is public access to horse trails in every part of the world. Horses are used for therapeutic purposes both in specialized para-equestrian competition as well as non-competitive riding to improve human health and emotional development.
Horses are driven in harness racing, at horse shows, in other types of exhibition such as historical reenactment or ceremony pulling carriages. In some parts of the world, they are still used for practical purposes such as farming. Horses continue to be used in public service: in traditional ceremonies and volunteer mounted patrols and for mounted search and rescue. Riding halls enable the training of horse and rider in all weathers as well as indoor competition riding. Though there is controversy over the exact date horses were domesticated and when they were first ridden, the best estimate is that horses first were ridden 3500 BC. Indirect evidence suggests. There is some evidence that about 3,000 BC, near the Dnieper River and the Don River, people were using bits on horses, as a stallion, buried there shows teeth wear consistent with using a bit. However, the most unequivocal early archaeological evidence of equines put to working use was of horses being driven. Chariot burials about 2500 BC present the most direct hard evidence of horses used as working animals.
In ancient times chariot warfare was followed by the use of war horses as heavy cavalry. The horse played an important role throughout human history all over the world, both in warfare and in peaceful pursuits such as transportation and agriculture. Horses died out at the end of the Ice Age. Horses were brought back to North America by European explorers, beginning with the second voyage of Columbus in 1493. Equestrianism was introduced in the 1900 Summer Olympics as an Olympic sport with jumping events. Humans appear to have long expressed a desire to know which horse or horses were the fastest, horse racing has ancient roots. Gambling on horse races appears to go hand-in hand with racing and has a long history as well. Thoroughbreds have the pre-eminent reputation as a racing breed, but other breeds race. Under saddle Thoroughbred horse racing is the most popular form worldwide. In the UK, it is governed by the Jockey Club in the United Kingdom. In the USA, horse racing is governed by The Jockey Club.
Steeplechasing involves racing on a track where the horses jump over obstacles. It is most common in the UK, where it is called National Hunt racing. American Quarter Horse racing—races over distances of a quarter-mile. Seen in the United States, sanctioned by the American Quarter Horse Association. Arabian horses, Akhal-Teke, American Paint Horses and other light breeds are raced worldwide. Endurance riding, a sport in which the Arabian horse dominates at the top levels, has become popular in the United States and in Europe; the Federation Equestre International governs international races, the American Endurance Ride Conference organizes the sport in North America. Endurance races take place over a given, measured distance and the horses have an start. Races are 50 to 100 miles, over mountainous or other natural terrain, with scheduled stops to take the horses' vital signs, check soundness and verify that the horse is fit to continue; the first horse to finish and be confirmed by the veterinarian as fit to continue is the winner.
Additional awards are given to the best-conditioned horses who finish in the top 10. Limited distance rides of about 25–20 miles are offered to newcomers. Ride and Tie. Ride and Tie involves three equal partners: one horse; the humans alternately ride. Show jumping: Show jumping is when a horse carries a rider over an obstacle commonly known as a jump. There are multiple jumps in a show, if the horse hits or refuses a jump, points will be deducted from the rider score; this is a timed event, the rider is expected to complete the course in a certain amount of time, without error. There are the hunter divisions. In the hunters, riders have to make their horses look good; the judges look at the quality of the course, if there are two or more riders who had put down amazing courses the judge or judges looks at how the horse looks and acts with the rider. In harness: Both light and heavy breeds as well as ponies are raced in harness with a sulk