Inbreeding
Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are related genetically. By analogy, the term is used in human reproduction, but more refers to the genetic disorders and other consequences that may arise from expression of deleterious or recessive traits resulting from incestuous sexual relationships and consanguinity. Inbreeding results in homozygosity, which can increase the chances of offspring being affected by deleterious or recessive traits; this leads to at least temporarily decreased biological fitness of a population, its ability to survive and reproduce. An individual who inherits such deleterious traits is colloquially referred to as inbred; the avoidance of expression of such deleterious recessive alleles caused by inbreeding, via inbreeding avoidance mechanisms, is the main selective reason for outcrossing. Crossbreeding between populations often has positive effects on fitness-related traits, but sometimes leads to negative effects known as outbreeding depression.
However increased homozygosity increases probability of fixing beneficial alleles and slightly decreases probability of fixing deleterious alleles in population. Inbreeding can result in purging of deleterious alleles from a population through purifying selection. Inbreeding is a technique used in selective breeding. For example, in livestock breeding, breeders may use inbreeding when trying to establish a new and desirable trait in the stock and for producing distinct families within a breed, but will need to watch for undesirable characteristics in offspring, which can be eliminated through further selective breeding or culling. Inbreeding helps to ascertain the type of gene action affecting a trait. Inbreeding is used to reveal deleterious recessive alleles, which can be eliminated through assortative breeding or through culling. In plant breeding, inbred lines are used as stocks for the creation of hybrid lines to make use of the effects of heterosis. Inbreeding in plants occurs in the form of self-pollination.
Inbreeding can influence gene expression which can prevent inbreeding depression. Offspring of biologically related persons are subject to the possible effects of inbreeding, such as congenital birth defects; the chances of such disorders are increased when the biological parents are more related. This is because such pairings have a 25% probability of producing homozygous zygotes, resulting in offspring with two recessive alleles, which can produce disorders when these alleles are deleterious; because most recessive alleles are rare in populations, it is unlikely that two unrelated marriage partners will both be carriers of the same deleterious allele. It should be noted that for each homozygous recessive individual formed there is an equal chance of producing a homozygous dominant individual — one devoid of the harmful allele. Contrary to common belief, inbreeding does not in itself alter allele frequencies, but rather increases the relative proportion of homozygotes to heterozygotes. In the short term, incestuous reproduction is expected to increase the number of spontaneous abortions of zygotes, perinatal deaths, postnatal offspring with birth defects.
The advantages of inbreeding may be the result of a tendency to preserve the structures of alleles interacting at different loci that have been adapted together by a common selective history. Malformations or harmful traits can stay within a population due to a high homozygosity rate, this will cause a population to become fixed for certain traits, like having too many bones in an area, like the vertebral column of wolves on Isle Royale or having cranial abnormalities, such as in Northern elephant seals, where their cranial bone length in the lower mandibular tooth row has changed. Having a high homozygosity rate is problematic for a population because it will unmask recessive deleterious alleles generated by mutations, reduce heterozygote advantage, it is detrimental to the survival of small, endangered animal populations; when deleterious recessive alleles are unmasked due to the increased homozygosity generated by inbreeding, this can cause inbreeding depression. There may be other deleterious effects besides those caused by recessive diseases.
Thus, similar immune systems may be more vulnerable to infectious diseases. Inbreeding history of the population should be considered when discussing the variation in the severity of inbreeding depression between and within species. With persistent inbreeding, there is evidence that shows that inbreeding depression becomes less severe; this is associated with the unmasking and elimination of deleterious recessive alleles. However, inbreeding depression is not a temporary phenomenon because this elimination of deleterious recessive alleles will never be complete. Eliminating deleterious mutations through inbreeding under moderate selection is not as effective. Fixation of alleles most occurs through Muller's ratchet, when an asexual population's genome accumulates deleterious mutations that are irreversible. Despite all its disadvantages, inbreeding can have a variety of advantages, such as reducing the recombination load, allowing the expression of recessive advantageous phenotypes, it has been proposed th
Cattle
Cattle—colloquially cows—are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, are most classified collectively as Bos taurus. Cattle are raised as livestock for meat, for milk, for hides, which are used to make leather, they are used as riding animals and draft animals. Another product of cattle is dung, which can be used to create fuel. In some regions, such as parts of India, cattle have significant religious meaning. Cattle small breeds such as the Miniature Zebu, are kept as pets. Around 10,500 years ago, cattle were domesticated from as few as 80 progenitors in central Anatolia, the Levant and Western Iran. According to an estimate from 2011, there are 1.4 billion cattle in the world. In 2009, cattle became one of the first livestock animals to have a mapped genome; some consider cattle the oldest form of wealth, cattle raiding one of the earliest forms of theft. Cattle were identified as three separate species: Bos taurus, the European or "taurine" cattle.
The aurochs is ancestral to both taurine cattle. These have been reclassified as one species, Bos taurus, with three subspecies: Bos taurus primigenius, Bos taurus indicus, Bos taurus taurus. Complicating the matter is the ability of cattle to interbreed with other related species. Hybrid individuals and breeds exist, not only between taurine cattle and zebu, but between one or both of these and some other members of the genus Bos – yaks and gaur. Hybrids such as the beefalo breed can occur between taurine cattle and either species of bison, leading some authors to consider them part of the genus Bos, as well; the hybrid origin of some types may not be obvious – for example, genetic testing of the Dwarf Lulu breed, the only taurine-type cattle in Nepal, found them to be a mix of taurine cattle and yak. However, cattle cannot be hybridized with more distantly related bovines such as water buffalo or African buffalo; the aurochs ranged throughout Europe, North Africa, much of Asia. In historical times, its range became restricted to Europe, the last known individual died in Mazovia, Poland, in about 1627.
Breeders have attempted to recreate cattle of similar appearance to aurochs by crossing traditional types of domesticated cattle, creating the Heck cattle breed. The noun cattle encompasses both sexes; the singular, technically means the female, the male being bull. The plural form cows is sometimes used colloquially to refer to both sexes collectively, as e.g. in a herd, but that usage can be misleading as the speaker's intent may indeed be just the females. The bovine species per se is dimorphic. Cattle did not originate as the term for bovine animals, it was borrowed from Anglo-Norman catel, itself from medieval Latin capitale'principal sum of money, capital', itself derived in turn from Latin caput'head'. Cattle meant movable personal property livestock of any kind, as opposed to real property; the word is a variant of chattel and related to capital in the economic sense. The term replaced earlier Old English feoh ` property', which survives today as fee; the word "cow" came via Anglo-Saxon cū, from Common Indo-European gʷōus = "a bovine animal", compare Persian: gâv, Sanskrit: go-, Welsh: buwch.
The plural cȳ became ki or kie in Middle English, an additional plural ending was added, giving kine, but kies and others. This is the origin of the now archaic English plural, "kine"; the Scots language singular is coo or cou, the plural is "kye". In older English sources such as the King James Version of the Bible, "cattle" refers to livestock, as opposed to "deer" which refers to wildlife. "Wild cattle" may refer to undomesticated species of the genus Bos. Today, when used without any other qualifier, the modern meaning of "cattle" is restricted to domesticated bovines. In general, the same words are used in different parts of the world, but with minor differences in the definitions; the terminology described here contrasts the differences in definition between the United Kingdom and other British-influenced parts of the world such as Canada, New Zealand and the United States. An "intact" adult male is called a bull. A wild, unmarked bull is known as a micky in Australia. An unbranded bovine of either sex is called a maverick in the Canada.
An adult female that has had a calf is a cow. A young female before she has had a calf of her own and is under three years of age is called a heifer. A young female that has had only one calf is called a first-calf heifer. Young cattle of both sexes are called calves until they are weaned weaners until they are a year old in some areas. After that, they are referred to as stirks if between one and two years of age. A castrated male is called a steer in the United States.
Hybrid (biology)
In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents, but can show hybrid vigour, sometimes growing larger or taller than either parent; the concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how related the parent species are. Species are reproductively isolated by strong barriers to hybridisation, which include morphological differences, differing times of fertility, mating behaviors and cues, physiological rejection of sperm cells or the developing embryo; some act before fertilization and others after it. Similar barriers exist in plants, with differences in flowering times, pollen vectors, inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and the structure of the chromosomes.
A few animal species and many plant species, are the result of hybrid speciation, including important crop plants such as wheat, where the number of chromosomes has been doubled. Human impact on the environment has resulted in an increase in the interbreeding between regional species, the proliferation of introduced species worldwide has resulted in an increase in hybridisation; this genetic mixing may threaten many species with extinction, while genetic erosion in crop plants may be damaging the gene pools of many species for future breeding. A form of intentional human-mediated hybridisation is the crossing of wild and domesticated species; this is common in modern agriculture. One such flower, Oenothera lamarckiana, was central to early genetics research into mutationism and polyploidy, it is more done in the livestock and pet trades. Human selective breeding of domesticated animals and plants has resulted is the development of distinct breeds. Hybrid humans existed in prehistory. For example and anatomically modern humans are thought to have interbred as as 40,000 years ago.
Mythological hybrids appear in human culture in forms as diverse as the Minotaur, blends of animals and mythical beasts such as centaurs and sphinxes, the Nephilim of the Biblical apocrypha described as the wicked sons of fallen angels and attractive women. The term hybrid is derived from Latin hybrida, used for crosses such as of a tame sow and a wild boar; the term came into popular use in English in the 19th century, though examples of its use have been found from the early 17th century. Conspicuous hybrids are popularly named with portmanteau words, starting in the 1920s with the breeding of tiger–lion hybrids. From the point of view of animal and plant breeders, there are several kinds of hybrid formed from crosses within a species, such as between different breeds. Single cross hybrids result from the cross between two true-breeding organisms which produces an F1 hybrid; the cross between two different homozygous lines produces an F1 hybrid, heterozygous. The F1 generation is phenotypically homogeneous, producing offspring that are all similar to each other.
Double cross hybrids result from the cross between two different F1 hybrids. Three-way cross hybrids result from the cross between an inbred line. Triple cross hybrids result from the crossing of two different three-way cross hybrids. Top cross hybrids result from the crossing of a top quality or pure-bred male and a lower quality female, intended to improve the quality of the offspring, on average. Population hybrids result from the crossing of plants or animals in one population with those of another population; these crosses between different breeds. In horticulture, the term stable hybrid is used to describe an annual plant that, if grown and bred in a small monoculture free of external pollen produces offspring that are "true to type" with respect to phenotype. Hybridisation can occur in the hybrid zones where the geographical ranges of species, subspecies, or distinct genetic lineages overlap. For example, the butterfly Limenitis arthemis has two major subspecies in North America, L. a. arthemis and L. a. astyanax.
The white admiral has a bright, white band on its wings, while the red-spotted purple has cooler blue-green shades. Hybridisation occurs between a narrow area across New England, southern Ontario, the Great Lakes, the "suture region", it is at these regions. Other hybrid zones have formed between described species of animals. From the point of view of genetics, several different kinds of hybrid can be distinguished. A genetic hybrid carries two different alleles of the same gene, where for instance one allele may code for a lighter coat colour than the other. A structural hybrid results from the fusion of gametes that have differing structure in at least one chromosome, as a result of structural abnormalities. A numerical hybrid results from the fusion of gamet
Canid hybrid
Canid hybrids are the result of interbreeding between different species of the canine family. They occur in the wild, in particular between domestic or feral dogs and wild native canids; the wolf-like canids are a group of large carnivores that are genetically related because their chromosomes number 78. The group includes genus Canis and Lycaon; the members are the dog, gray wolf, golden jackal, Ethiopian wolf, black-backed jackal, side-striped jackal and African wild dog. Newly proposed members include the red wolf, eastern wolf, African golden wolf; as they possess 78 chromosomes, all members of the genus Canis are karyologically indistinguishable from each other, from the dhole and the African hunting dog. The members of Canis can interbreed; when the differences in number and arrangement of chromosomes is too great, hybridization becomes less and less likely. The wolf, dog and golden jackal all have 78 chromosomes arranged in 39 pairs; this allows them to hybridize and produce fertile offspring.
There are two exceptions: the side-striped black-backed jackal. Although these two theoretically could interbreed with each other to produce fertile offspring, it appears they cannot hybridize with the rest of the genus Canis. A study of the maternal mitochondrial DNA of the black-backed jackal could find no evidence of genotypes from the most mates - the side-striped jackal nor the golden jackal - indicating that male black-backed jackals had not bred with these. There is no evidence. Other members of the wider dog family, the Canidae, such as South American canids, true foxes, bat-eared foxes, or raccoon dogs which diverged seven to ten million years ago, are less related to and cannot hybridize with the wolf-like canids because the red fox has 34 metacentric chromosomes and from 0 to 8 small B chromosomes, the raccoon dog has 42 chromosomes, the fennec fox has 64 chromosomes. Dog hybrids kept as pets are prohibited in certain jurisdictions, or are classed as wild animals and must be housed in the same way as purebred wolves.
In the United States legislation differs from state to state. In New York, the law does not allow an individual to house or own a dog hybrid of any kind if there is a low percentage of wolf genes in the hybrid. States such as Indiana and Arkansas allow the ownership of hybrid animals, but they regulate it with health records, immunization records, registration of the animal while other states, such as Arizona, do not have any laws about owning a wolfdog hybrid. States may not create their own laws regarding the issue of wolfdog hybrids; the domestic dog is a domesticated form of the gray wolf and therefore belongs to the same species as other wolves, such as the dingo. Therefore, crosses between these sub-species are biologically unremarkable and not a hybridization in the same sense as an interbreeding between different species of Canidae. Wolves are different from domestic dogs in that wolves have slimmer chests, longer legs, they have stronger jaws than those of the domestic subspecies; the difference in appearance from the wolf to the domestic dog becomes larger when a mix of the two animals is created.
Wolfdogs do not have one common description of their appearance because it varies from one breeding cycle to the next. It differs from cycle to cycle because the number of wolf genes inherited in the animal differs and is recorded in a percentage form; the general layout for describing the percentage of wolfdogs is as follows: 1-49% is considered low content, 50-74% is considered to be mid-content, 75% and higher is considered to be high content. The percentage of the amount of wolf in a wolfdog decides. For example, if a wolfdog is 25% husky and 75% wolf, it will appear more like a wolf than a husky because it contains more genes from the wolf; this means that the appearance of the wolfdog will most contain a narrower chest, longer legs, sharper teeth because it inherited more traits from the wolf parent. People wanting to improve domestic dogs or create an exotic pet may breed domestic dogs to wolves. Gray wolves have been crossed with dogs that have a wolf-like appearance, such as Siberian huskies, Alaskan malamutes.
The breeding of wolf–dog crosses is controversial, with opponents purporting that it produces an animal unfit as a domestic pet. A number of wolfdog breeds are in development; the first generation crosses are backcrossed to domestic dogs to maintain a domestic temperament and consistent conformation. The dingo breeds with other domestic dogs; this is now so widespread that in some areas, dingoes are now mixed-breed dogs, crossed in recent times with dogs from other parts of the world. However, DNA study shows that "the dingo originates from domesticated dogs from East Asia" and so interbreeding between dingos and other domestic dogs is not a hybridization in the same sense as an interbreeding between different species of Canidae; some dingo hybrids are accepted back into the wild dingo population, where they breed with pure dingoes. In some parts of Australia, up to 80% of dingoes are part domestic dog. Dingoes are distinguishable from domestic dogs through DNA and through having longer teeth and longer m
National Show Horse
The National Show Horse originated as a part-Arabian cross between an American Saddlebred and an Arabian horse. It is now established as a separate breed, since the founding of a breed registry in August 1981. Registered animals today may be the offspring of registered NSH parents or may be a combination between an American Saddlebred, a National Show Horse. Non-NSH mares and stallions must be registered with their appropriate registries, stallions who are Arabian or Saddlebred must additionally be nominated and approved by the NSHR board of directors. Although any combination of these three breeds may be used, as of December 1, 2009 there must be at least 50% Arabian blood in the horse to be registered, up to 99% Arabian blood; the National Show Horse combines the refinement of the Arabian with the animation of the Saddlebred. The resulting horse has the high-set, long, swan-like neck of the Saddlebred; the neck should not have a pronounced crest. The head is refined and small, with small ears and either a straight or concave profile.
The horses are close-coupled with a level topline and have a deep, laid back shoulder. The tail carriage is high; the NSH is 14.3-16.2 hands tall, with some individuals over or under. The NSH may be a variety of colors, including the traditional bay, gray and black of the Arabian, with Saddlebred ancestry adding a broader range of color than seen in the Arabian breed, most notably and palomino; the National Show Horse is most used for saddle seat riding. They are horses with high-stepping action and can be trained to move with a elevated front end; some can be trained to be five-gaited, adding the slow gait and rack to the traditional gaits of the walk and canter. A versatile breed, they can be used for show jumping, dressage, or western riding. Dutson, Judith Storey's Illustrated Guide to 96 Horse Breeds of North America North Adams, Mass.: Storey Pub 2005 ISBN 1-58017-612-7 NSHR Press Release Is Your Horse Now Eligible for NSH Registration? The Arabian Horse Association The National Show Horse Registry
Dog crossbreed
Crossbreed dogs or designer dogs are dogs which have been intentionally bred from two or more recognized dog breeds and not from dogs with no purebred ancestors, but have not been artificially bred to each other enough to breed true and be recognized as a breed in their own right. Several unofficially recognized crossbreed types date from the 14th century or earlier, such as the lurcher or the longdog; the Encyclopædia Britannica traces the term "designer dog" to the late 20th century, when breeders began to cross purebred poodles with other purebred breeds in order to obtain a dog with the poodles' hypoallergenic coat, along with various desirable characteristics from other breeds. The primary identifying mark of a crossbred "designer dog" is that the resulting puppies are called by a portmanteau word made up of syllables from the breed names of the two purebred parents, such as Schnoodle. Or Shepsky. Other purebred breeds are being crossed to provide designer dogs described with an endless range of created labels, such as the Puggle.
There are complex crosses being labeled in this manner, such as German Chusky. Like children in a family, a percentage of designer dogs with the same breed ancestry will look similar to each other though crossbreeding does not result in as uniform a phenotype as the breeding of purebreds. Pups in the same litter will look quite different. Another defining characteristic of designer dogs is that they are bred as companions and pets. Working and hunting dogs deliberately crossbred for a particular working purpose are not given portmanteau names; these dogs could be considered only as cross breeds, not as designer animals, since appearance is not the main reason for them to be bred. An exception to this is the Labradoodle, which although having a Portmanteau name, is used as a Guide or Assistance dog as well as being popular family dogs. Although designer dogs are selected by owners for their novelty, reputable breeders sometimes use crossbreeding in an attempt to reduce the incidence of certain hereditary problems found in the purebred breeds, while retaining their more appealing traits.
Jon Mooallem in The New York Times writes, "Given the 350 inherited disorders littering the dog genome, crossing two purebreds and expanding their gene pools can be'a phenomenally good idea,' according to one canine geneticist—if it is done conscientiously." Crossbreeding has not been well studied in dogs. The heritability of the desired trait being bred for needs to be known. In addition, the goals of dog crossbreeding may be harder to define than the goals of livestock crossbreeding. Designer dog breeders are criticised for being more interested in profitable puppy production than in dog health and welfare. Wally Conron comments on the popularity of crosses after his introduction of the Labradoodle: "Were breeders bothering to check their sires and bitches for heredity faults, or were they caught up in delivering to hungry customers the next status symbol?" Designer dog puppies sometimes bring higher prices than the purebreds. The fanciers of designer dogs respond that all modern dog breeds were created from earlier breeds and types of dogs through the same kind of selective breeding, used to create designer dogs.
The Toy Poodle was bred down in size from larger poodles, most by crossing with various small Bichon types, such as the Maltese and Havanese. Most of the modern breeds have ancestries that include various older dog breeds. Health of crossbred dog depends on their being descended from healthy parents. Breeders who select their breeding stock for cost-effectiveness and who skip health testing for the same reason will not produce puppies that are as reliably healthy as those bred by more conscientious breeders. However, studies of longevity in dogs have found some advantage for crossbreeds compared to purebred dogs. "There was a significant correlation between body longevity. Crossbreeds lived longer than average but several pure breeds lived longer than cross breeds, notably Jack Russell, miniature poodles and whippets". In general it is believed that crossbred dogs "have a far lower chance of exhibiting the disorders that are common with the parental breeds, their genetic health will be higher."Many breeders of designer dogs take advantage of the fact that people are impressed by a pet that they believe offers them an elevated social status, such as other "designer" goods do.
"It's human nature to aspire to own something a little different, a little fancy or in short supply." Crossbreeding to take advantage of the increased chance that a recessive detrimental allele will only be inherited from one parent, therefore not expressed in the phenotype of the offspring, is only one strategy breeders can use to decrease the incidences of genetic defects. Knowing the disease incidence in the breed, the genetic history of the individual, is important in dog breeding. Having the parental dogs genetically tested for defects known to be troublesome to their breed (or breeds
Designer crossbreed
A designer crossbreed or designer breed is a crossbred animal that has purebred parents registered with a breed registry, but from two different breeds. These animals are the result of a deliberate decision to create a specific crossbred animal. Less the animal may have more than two pure breeds in its ancestry, but unlike a mutt or a mongrel, its entire pedigree is known to descend from specific known animals. While the term is best-known when applied to certain dog crossbreeds, other animals such as cattle, horses and cats may be bred in this fashion; some crossbred breeders start a freestanding breed registry to record designer crossbreds, other crossbreds may be included in an "appendix" to an existing purebred registry. Either form of registration may be the first step in recording and tracking pedigrees in order to develop a new breed; the purpose of creating designer crossbreds is one or more of the following reasons: To breed animals with Heterosis known as "hybrid vigor." To create animals with more predictable characteristics than mixed breed or mongrel breeding To avoid certain undesirable recessive traits that lead to genetic diseases that plague many purebred animals.
To develop an animal that combines what are viewed as the best traits of two or more breeds. As the preliminary steps toward developing a new animal breed. Breeders of designer crossbreds borrow the technical language from hybrid plant breeding: A first generation, 50-50 crossbred is an F1 cross. Subsequent generations may see a purebred animal crossed back on a crossbred, creating a 75/25 cross, or a BC1 or F1b "backcross." The breeding of two crossbreds of the same combination of breeds, creating a F2 cross, an animal, still a 50-50 cross, but it is the second filial generation of the combination. A F2 cross bred to an F2 cross creates a F3 cross. A F2 animal bred to an F1 animal creates a F2b backcross. F3 crosses and greater are called "multi-generational" crosses. In dog breeding, three generations of reliable documented breeding can be considered a "breed" rather than a crossbreed. There are disadvantages to creating designer crossbreds, notably the potential that the cross will be of inferior quality or that it will not produce as consistent a result as would breeding purebred animals.
For example, the poodle is a frequent breed used in creation of designer crossbreds, due to its nonshedding coat, but that trait does not always breed true when it is part of a designer cross. Because breeders of crossbred animals may be less careful about genetic testing and weeding out undesirable traits, certain deleterious dominant genes may still be passed on to a crossbred offspring. In an F2 cross, recessive genetic traits may return if the parent animals were both carriers of an undesired trait. Crossbreed Designer dog Grade horse Open stud book dogbreedinfo.com idcba.org
