91-450: A white tiger is a tiger with a genetic condition affecting its pelt's pigmentation. White tiger , White Tiger or The White Tiger may also refer to: White tiger The white tiger , or bleached tiger , is a leucistic morph of the tiger . It is reported in the wild from time to time in the Indian states of Madhya Pradesh , Assam , West Bengal , Bihar , Odisha , in
182-581: A population (called inbreeding depression ), which is 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 sometimes has positive effects on fitness-related traits, but also sometimes leads to negative effects known as outbreeding depression . However, increased homozygosity increases
273-455: A population bottleneck caused by purposeful ( assortative ) breeding or natural environmental factors, the deleterious inherited traits are culled. Island species are often very inbred, as their isolation from the larger group on a mainland allows natural selection to work on their population. This type of isolation may result in the formation of race or even speciation , as the inbreeding first removes many deleterious genes, and permits
364-450: A species may not be able to adapt to changes in environmental conditions. Each individual will have similar immune systems, as immune systems are genetically based. When a species becomes endangered , the population may fall below a minimum whereby the forced interbreeding between the remaining animals will result in extinction . Natural breedings include inbreeding by necessity, and most animals only migrate when necessary. In many cases,
455-513: A TYR mutation is responsible for the white lion leucistic variant, a normal TYR gene was found in both white tigers and snow leopards . Instead, in white tigers, a naturally-occurring point mutation in the SLC45A2 transport protein gene was found to underlie its pigmentation. The resultant single amino acid substitution introduces an alanine residue that protrudes into the transport protein's central passageway, apparently blocking it, and by
546-436: A consistent and uniform animal model for experimental purposes and enables genetic studies in congenic and knock-out animals. In order to achieve a mouse strain that is considered inbred, a minimum of 20 sequential generations of sibling matings must occur. With each successive generation of breeding, homozygosity in the entire genome increases, eliminating heterozygous loci. With 20 generations of sibling matings, homozygosity
637-467: A form of distant linebreeding occurs. Again it is up to the assortative breeder to know what sort of traits, both positive and negative, exist within the diversity of one breeding. This diversity of genetic expression, within even close relatives, increases the variability and diversity of viable stock. Systematic inbreeding and maintenance of inbred strains of laboratory mice and rats is of great importance for biomedical research. The inbreeding guarantees
728-463: A group of orange tigers from outcrosses which were bought by a Pakistani senator and shipped to Pakistan. Rajiv, Pretoria Zoo's white tiger, who was born in the Cincinnati Zoo, was also outcrossed and sired at least two litters of orange cubs at Pretoria Zoo. Outcrossing is not necessarily done with the intent of producing more white cubs by resuming inbreeding further down the line. Outcrossing
819-469: A healthier strain of white tigers. The Indian government reportedly considered the offer; however, India had a moratorium on breeding white tigers after cubs were born at New Delhi Zoo with arched backs and clubbed feet, necessitating euthanasia . Siegfried & Roy have bred white tigers in collaboration with the Nashville Zoo . To better preserve genetic diversity and avoid genetic defects,
910-439: A large fraction of their alleles, the probability that any such deleterious allele is inherited from the common ancestor through both parents is increased dramatically. For each homozygous recessive individual formed there is an equal chance of producing a homozygous dominant individual — one completely devoid of the harmful allele. Contrary to common belief, inbreeding does not in itself alter allele frequencies, but rather increases
1001-437: A large white tiger, died just short of his 20th birthday, an enviable age for a male of any subspecies, since most males live shorter captive lives. Premature deaths in other collections may be artifacts of captive environmental conditions...in 52 births we had four stillbirths, one of which was an unexplained loss. We lost two additional cubs from viral pneumonia, which is not excessive. Without data from non-inbred tiger lines, it
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#17328017024761092-493: A mechanism yet to be determined, this prevents pheomelanin expression in the fur. Mutations in the same gene are known to result in 'cream' coloration in horses, and play a role in the paler skin of humans of European descent. This is a recessive trait , meaning that it is only seen in individuals that are homozygous for this mutation, and that while the progeny of white tigers will all be white, white tigers can be also bred from colored Bengal tiger pairs in which each possesses
1183-404: A particular recessive genetic mutation . Except in certain rare circumstances, such as new mutations or uniparental disomy , both parents of an individual with such a disorder will be carriers of the gene. These carriers do not display any signs of the mutation and may be unaware that they carry the mutated gene. Since relatives share a higher proportion of their genes than do unrelated people, it
1274-468: A recessive gene to become homozygous and produce the stripeless phenotype. About one fourth of Bhim and Sumita's offspring were stripeless. Their striped white offspring, which have been sold to zoos around the world, may also carry the gene for the stripeless trait. Because Tony's genome is present in many white tiger pedigrees, the gene may also be present in other captive white tigers. As a result, stripeless white tigers have appeared in zoos as far afield as
1365-462: A severe winter weather related population crash. These studies show that inbreeding depression and ecological factors have an influence on survival. The Florida panther population was reduced to about 30 animals, so inbreeding became a problem. Several females were imported from Texas and now the population is better off genetically. A measure of inbreeding of an individual A is the probability F (A) that both alleles in one locus are derived from
1456-566: A significantly higher chance of reaching repeated results with future offspring. Additionally, consanguineous parents possess a high risk of premature birth and producing underweight and undersized infants. Viable inbred offspring are also likely to be inflicted with physical deformities and genetically inherited diseases. Studies have confirmed an increase in several genetic disorders due to inbreeding such as blindness, hearing loss, neonatal diabetes, limb malformations, disorders of sex development , schizophrenia and several others. Moreover, there
1547-574: A single copy of the unique mutation. Inbreeding promotes recessive traits and has been used as a strategy to produce white tigers in captivity, but this has also resulted in a range of other genetic defects. The stripe color varies due to the influence and interaction of other genes. Another genetic characteristic makes the stripes of the tiger very pale; white tigers of this type are called snow-white or "pure white". White tigers, Siamese cats , and Himalayan rabbits have enzymes in their fur which react to temperature, causing them to grow darker in
1638-499: A small colony was discovered in the Point Sur region in the 1930s. Since then, the population has grown and spread along the central Californian coast to around 2,000 individuals, a level that has remained stable for over a decade. Population growth is limited by the fact that all Californian sea otters are descended from the isolated colony, resulting in inbreeding. Cheetahs are another example of inbreeding. Thousands of years ago,
1729-478: A small population for a period of time can lead to inbreeding within that population, resulting in increased genetic relatedness between breeding individuals. Inbreeding depression can also occur in a large population if individuals tend to mate with their relatives, instead of mating randomly. Due to higher prenatal and postnatal mortality rates, some individuals in the first generation of inbreeding will not live on to reproduce. Over time, with isolation, such as
1820-601: A tiger he sold to Marwell Zoo in England developed white spots, and bred them accordingly. The Lowry Park Zoo in Tampa Bay had four of these white Amur tigers, descended from Robert Baudy's stock. It has also been possible to expand the white-gene pool by outcrossing white tigers with unrelated orange tigers and then using the cubs to produce more white tigers. The white tigers Ranjit, Bharat, Priya and Bhim were all outcrossed, in some instances to more than one tiger. Bharat
1911-402: Is a way of bringing fresh blood into the white strain. The New Delhi Zoo loaned out white tigers to some of India's better zoos for outcrossing, and the government had to impose a whip to force zoos to return either the white tigers or their orange offspring. Siegfried & Roy performed at least one outcross. In the mid-1980s they offered to work with the Indian government in the creation of
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#17328017024762002-488: Is also denoted as the kinship coefficient between A and B. A particular case is the self-coancestry of individual A with itself, f(A,A), which is the probability that taking one random allele from A and then, independently and with replacement, another random allele also from A, both are identical by descent. Since they can be identical by descent by sampling the same allele or by sampling both alleles that happen to be identical by descent, we have f(A,A) = 1/2 + F(A)/2. Both
2093-576: Is an increased risk for congenital heart disease depending on the inbreeding coefficient (See coefficient of inbreeding ) of the offspring, with significant risk accompanied by an F =.125 or higher. The general negative outlook and eschewal of inbreeding that is prevalent in the Western world today has roots from over 2000 years ago. Specifically, written documents such as the Bible illustrate that there have been laws and social customs that have called for
2184-492: Is difficult to determine whether this number is high or low with any degree of accuracy." Ed Maruska also addressed the issue of deformities: "Other than a case of hip dysplasia that occurred in a male white tiger, we have not encountered any other body deformities or any physiological or neurological disorders. Some of these reported maladies in mutant tigers in other collections may be a direct result of inbreeding or improper rearing management of tigers generally." Because of
2275-486: Is directly linked to reduced pigmentation in white tigers. An additional genetic condition can result in near-complete absence of stripes, making the tiger almost pure white. One such specimen was exhibited at Exeter Change in England in 1820, and described by Georges Cuvier as "A white variety of Tiger is sometimes seen, with the stripes very opaque, and not to be observed except in certain angles of light." Naturalist Richard Lydekker said that, "a white tiger, in which
2366-613: Is discussed in the following quotation on cattle: Meanwhile, milk production per cow per lactation increased from 17,444 lbs to 25,013 lbs from 1978 to 1998 for the Holstein breed. Mean breeding values for milk of Holstein cows increased by 4,829 lbs during this period. High producing cows are increasingly difficult to breed and are subject to higher health costs than cows of lower genetic merit for production (Cassell, 2001). Intensive selection for higher yield has increased relationships among animals within breed and increased
2457-493: Is due to their inability to produce normal tyrosinase, a trait they share with albinos, according to zoo veterinarian David Taylor . He treated a pair of white tigers from the Cincinnati Zoo at Fritz Wurm's safari park in Stukenbrock, Germany, for salmonella poisoning, which reacted strangely to the anaesthesia. Mohini was checked for Chédiak–Higashi syndrome in 1960, but the results were inconclusive. This condition
2548-469: Is more likely that related parents will both be carriers of the same recessive allele, and therefore their children are at a higher risk of inheriting an autosomal recessive genetic disorder. The extent to which the risk increases depends on the degree of genetic relationship between the parents; the risk is greater when the parents are close relatives and lower for relationships between more distant relatives, such as second cousins, though still greater than for
2639-404: Is not as effective. Fixation of alleles most likely occurs through Muller's ratchet , when an asexual population's genome accumulates deleterious mutations that are irreversible. Despite all its disadvantages, inbreeding can also have a variety of advantages, such as ensuring a child produced from the mating contains, and will pass on, a higher percentage of its mother/father's genetics, reducing
2730-409: Is occurring at roughly 98.7% of all loci in the genome, allowing for these offspring to serve as animal models for genetic studies. The use of inbred strains is also important for genetic studies in animal models, for example to distinguish genetic from environmental effects. The mice that are inbred typically show considerably lower survival rates. Inbreeding increases homozygosity, which can increase
2821-551: Is primarily assortative breeding (see selective breeding ). Without the sorting of individuals by trait, a breed could not be established, nor could poor genetic material be removed. Homozygosity is the case where similar or identical alleles combine to express a trait that is not otherwise expressed (recessiveness). Inbreeding exposes recessive alleles through increasing homozygosity. Breeders must avoid breeding from individuals that demonstrate either homozygosity or heterozygosity for disease causing alleles. The goal of preventing
White tiger (disambiguation) - Misplaced Pages Continue
2912-426: Is similar to albino mutations and causes bluish lightening of the fur color, crossed eyes, and prolonged bleeding after surgery. Also, in the event of an injury, the blood is slow to coagulate. This condition has been observed in domestic cats, but there has never been a case of a white tiger having Chédiak–Higashi syndrome. There has been a single case of a white tiger having central retinal degeneration , reported from
3003-629: The Association of Zoos and Aquariums barred member zoos from intentionally breeding to produce white tigers, white lions , or king cheetahs in a white paper adopted by the board of directors in July 2011. The paper explains that selecting for or against any particular allele would result in a loss of genetic diversity. Instead, the alleles should be maintained at their natural frequencies. Inbreeding to produce abnormal appearances can also produce congenital defects that impact health and welfare. Sometimes
3094-574: The Crater lions, it is known that a population bottleneck has occurred. Researchers found far greater genetic heterozygosity than expected. In fact, predators are known for low genetic variance, along with most of the top portion of the trophic levels of an ecosystem . Additionally, the alpha males of two neighboring prides can be from the same litter; one brother may come to acquire leadership over another's pride, and subsequently mate with his 'nieces' or cousins. However, killing another male's cubs, upon
3185-476: The Czech Republic ( Liberec ), Spain and Mexico. Stage magicians Siegfried & Roy were the first to attempt to selectively breed for stripeless tigers; they owned snow-white Bengal tigers taken from Cincinnati Zoo (Tsumura, Mantra, Mirage and Akbar-Kabul) and Guadalajara , Mexico (Vishnu and Jahan), as well as a stripeless Siberian tiger called Apollo. In 2004, a blue-eyed, stripeless white tiger
3276-629: The South American sea lion , there was concern that recent population crashes would reduce genetic diversity. Historical analysis indicated that a population expansion from just two matrilineal lines was responsible for most of the individuals within the population. Even so, the diversity within the lines allowed great variation in the gene pool that may help to protect the South American sea lion from extinction. In lions, prides are often followed by related males in bachelor groups. When
3367-521: The Sunderbans region and especially in the former State of Rewa . It has the typical black stripes of a tiger, but its coat is otherwise white or near-white, and it has blue eyes. The white Bengal tigers are distinctive due to the color of their fur. The white fur is caused by a lack of the pigment pheomelanin , which is found in Bengal tigers with orange color fur. When compared to Bengal tigers,
3458-569: The recombination load , and allowing the expression of recessive advantageous phenotypes. Some species with a Haplodiploidy mating system depend on the ability to produce sons to mate with as a means of ensuring a mate can be found if no other male is available. It has been proposed that under circumstances when the advantages of inbreeding outweigh the disadvantages, preferential breeding within small groups could be promoted, potentially leading to speciation . Autosomal recessive disorders occur in individuals who have two copies of an allele for
3549-556: The British Queen Victoria or King Christian IX of Denmark . The House of Habsburg was known for its intermarriages; the Habsburg lip often cited as an ill-effect. The closely related houses of Habsburg, Bourbon , Braganza and Wittelsbach also frequently engaged in first-cousin unions as well as the occasional double-cousin and uncle–niece marriages. In ancient Egypt , royal women were believed to carry
3640-605: The Milwaukee County Zoo, which could be related to reduced pigmentation in the eye. The white tiger in question was a male named Mota on loan from the Cincinnati Zoo. There is a myth that white tigers have an 80% infant mortality rate. However, the infant mortality rate for white tigers is no higher than it is for normal orange tigers bred in captivity. Cincinnati Zoo director Ed Maruska said: "We have not experienced premature death among our white tigers. Forty-two animals born in our collection are still alive. Mohan,
3731-479: The Qatari population suffered from hereditary hearing loss; most were descendants of a consanguineous relationship. Inter-nobility marriage was used as a method of forming political alliances among elites. These ties were often sealed only upon the birth of progeny within the arranged marriage . Thus marriage was seen as a union of lines of nobility and not as a contract between individuals. Royal intermarriage
White tiger (disambiguation) - Misplaced Pages Continue
3822-481: The ability to make neither pheomelanin (red and yellow pigments) nor eumelanin (black and brown pigments), while a less severe mutation in the same gene in other mammals results in selective loss of pheomelanin, the so-called Chinchilla trait. The white phenotype in tigers had been attributed to such a Chinchilla mutation in tyrosinase, and in the past white tigers were sometimes referred to as 'partial albinos'. While whole genome sequencing determined that such
3913-425: The abstention from inbreeding. Along with cultural taboos, parental education and awareness of inbreeding consequences have played large roles in minimizing inbreeding frequencies in areas like Europe. That being so, there are less urbanized and less populated regions across the world that have shown continuity in the practice of inbreeding. The continuity of inbreeding is often either by choice or unavoidably due to
4004-448: The biological parents are more closely 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 partners will both be carriers of the same deleterious allele; however, because close relatives share
4095-532: The bloodlines and so it was advantageous for a pharaoh to marry his sister or half-sister; in such cases a special combination between endogamy and polygamy is found. Normally, the old ruler's eldest son and daughter (who could be either siblings or half-siblings) became the new rulers. All rulers of the Ptolemaic dynasty uninterruptedly from Ptolemy IV ( Ptolemy II married his sister but had no issue) were married to their brothers and sisters, so as to keep
4186-517: The chance for these recessive alleles to pair and become homozygous greatly increases, leading to offspring with autosomal recessive disorders. However, these deleterious effects are common for very close relatives but not for those related on the 3rd cousin or greater level, who exhibit increased fitness. Inbreeding is especially problematic in small populations where the genetic variation is already limited. By inbreeding, individuals are further decreasing genetic variation by increasing homozygosity in
4277-472: The chances of the expression of deleterious or beneficial recessive alleles and therefore has the potential to either decrease or increase the fitness of the offspring. Depending on the rate of inbreeding, natural selection may still be able to eliminate deleterious alleles. With continuous inbreeding, genetic variation is lost and homozygosity is increased, enabling the expression of recessive deleterious alleles in homozygotes. The coefficient of inbreeding , or
4368-439: The cheetah went through a population bottleneck that reduced its population dramatically so the animals that are alive today are all related to one another. A consequence from inbreeding for this species has been high juvenile mortality, low fecundity, and poor breeding success. In a study on an island population of song sparrows, individuals that were inbred showed significantly lower survival rates than outbred individuals during
4459-444: The closest available mate is a mother, sister, grandmother, father, brother, or grandfather. In all cases, the environment presents stresses to remove from the population those individuals who cannot survive because of illness. There was an assumption that wild populations do not inbreed; this is not what is observed in some cases in the wild. However, in species such as horses , animals in wild or feral conditions often drive off
4550-602: The cold. In the Bristol Zoo, a white tiger named Mohini was whiter than her relatives, who showed more cream tones. This may have been because she spent less time outdoors in the winter. Kailash Sankhala observed that white tigers were always whiter in Rewa State , even when they were born in New Delhi and returned there. "In spite of living in a dusty courtyard, they were always snow white." A weakened immune system
4641-434: The creation of hybrid lines to make use of the effects of heterosis . Inbreeding in plants also occurs naturally in the form of self-pollination . Inbreeding can significantly 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
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#17328017024764732-424: The degree of inbreeding in an individual, is an estimate of the percent of homozygous alleles in the overall genome. The more biologically related the parents are, the greater the coefficient of inbreeding, since their genomes have many similarities already. This overall homozygosity becomes an issue when there are deleterious recessive alleles in the gene pool of the family. By pairing chromosomes of similar genomes,
4823-399: The dominant male is killed or driven off by one of these bachelors, a father may be replaced by his son. There is no mechanism for preventing inbreeding or to ensure outcrossing. In the prides, most lionesses are related to one another. If there is more than one dominant male, the group of alpha males are usually related. Two lines are then being "line bred". Also, in some populations, such as
4914-405: The expression of genes that allow a population to adapt to an ecosystem . As the adaptation becomes more pronounced, the new species or race radiates from its entrance into the new space, or dies out if it cannot adapt and, most importantly, reproduce. The reduced genetic diversity , for example due to a bottleneck will unavoidably increase inbreeding for the entire population. This may mean that
5005-470: The extreme rarity of the white tiger allele in the wild, the breeding pool was limited to the small number of white tigers in captivity. According to Kailash Sankhala, the last white tiger ever seen in the wild was shot in 1958. Today there is a large number of white tigers in captivity. A white Amur tiger may have been born at Center Hill and has given rise to a strain of white Amur tigers. A man named Robert Baudy realized that his tigers had white genes when
5096-470: The forelegs, club foot , kidney problems, arched or crooked backbone and twisted neck. Reduced fertility and miscarriages, noted by "tiger man" Kailash Sankhala in pure-Bengal white tigers, were attributed to inbreeding depression . A condition known as "star-gazing" (the head and neck are raised almost straight up, as if the affected animal is gazing at the stars), which is associated with inbreeding in big cats, has also been reported in white tigers. There
5187-492: The fur was of a creamy tint, with the usual stripes faintly visible in certain parts, was exhibited at the old menagerie at Exeter Change about the year 1820." Hamilton Smith said, "A wholly white tiger, with the stripe-pattern visible only under reflected light, like the pattern of a white tabby cat, was exhibited in the Exeter Change Menagerie in 1820" and John George Wood stated that, "a creamy white, with
5278-400: The general population. Children of parent-child or sibling-sibling unions are at an increased risk compared to cousin-cousin unions. Inbreeding may result in a greater than expected phenotypic expression of deleterious recessive alleles within a population. As a result, first-generation inbred individuals are more likely to show physical and health defects, including: The isolation of
5369-409: The genetic diversity of a population and cause problems related to a too-small gene pool that may include an increased prevalence of genetic disorders and inbreeding depression. Outcrossing is where two unrelated individuals are crossed to produce progeny. In outcrossing, unless there is verifiable genetic information, one may find that all individuals are distantly related to an ancient progenitor. If
5460-411: The genomes of their offspring. Thus, the likelihood of deleterious recessive alleles to pair is significantly higher in a small inbreeding population than in a larger inbreeding population. The fitness consequences of consanguineous mating have been studied since their scientific recognition by Charles Darwin in 1839. Some of the most harmful effects known from such breeding includes its effects on
5551-506: The inbreeding and the coancestry coefficients can be defined for specific individuals or as average population values. They can be computed from genealogies or estimated from the population size and its breeding properties, but all methods assume no selection and are limited to neutral alleles. There are several methods to compute this percentage. The two main ways are the path method and the tabular method. Typical coancestries between relatives are as follows: Breeding in domestic animals
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#17328017024765642-710: The limitations of the geographical area. When by choice, the rate of consanguinity is highly dependent on religion and culture. In the Western world, some Anabaptist groups are highly inbred because they originate from small founder populations that have bred as a closed population. Of the practicing regions, Middle Eastern and northern Africa territories show the greatest frequencies of consanguinity. Among these populations with high levels of inbreeding, researchers have found several disorders prevalent among inbred offspring. In Lebanon , Saudi Arabia , Egypt , and in Israel ,
5733-696: 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, and 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 also be other deleterious effects besides those caused by recessive diseases. Thus, similar immune systems may be more vulnerable to infectious diseases (see Major histocompatibility complex and sexual selection ). Inbreeding history of
5824-550: The mortality rate as well as on the general health of the offspring. Since the 1960s, there have been many studies to support such debilitating effects on the human organism. Specifically, inbreeding has been found to decrease fertility as a direct result of increasing homozygosity of deleterious recessive alleles. Fetuses produced by inbreeding also face a greater risk of spontaneous abortions due to inherent complications in development. Among mothers who experience stillbirths and early infant deaths, those that are inbreeding have
5915-473: The negative health consequences of excessive inbreeding. Linebreeding is a form of inbreeding. There is no clear distinction between the two terms, but linebreeding may encompass crosses between individuals and their descendants or two cousins. This method can be used to increase a particular animal's contribution to the population. While linebreeding is less likely to cause problems in the first generation than does inbreeding, over time, linebreeding can reduce
6006-568: The offspring of consanguineous relationships have an increased risk of congenital malformations, congenital heart defects, congenital hydrocephalus and neural tube defects . Furthermore, among inbred children in Palestine and Lebanon, there is a positive association between consanguinity and reported cleft lip/palate cases. Historically, populations of Qatar have engaged in consanguineous relationships of all kinds, leading to high risk of inheriting genetic diseases. As of 2014, around 5% of
6097-473: The ordinary tigerine stripes so faintly marked that they were only visible in certain lights." Edwin Henry Landseer also drew this tigress in 1824. The modern strain of snow white tigers came from repeated brother–sister matings of Bhim and Sumita at Cincinnati Zoo . The gene involved may have come from a Siberian tiger , their part-Siberian ancestor Tony. Continued inbreeding appears to have caused
6188-572: The population should also 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 severely deleterious recessive alleles. However, inbreeding depression is not a temporary phenomenon because this elimination of deleterious recessive alleles will never be complete. Eliminating slightly deleterious mutations through inbreeding under moderate selection
6279-424: The probability of fixing beneficial alleles and also slightly decreases the probability of fixing deleterious alleles in a 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
6370-440: The rate of casual inbreeding. Many of the traits that affect profitability in crosses of modern dairy breeds have not been studied in designed experiments. Indeed, all crossbreeding research involving North American breeds and strains is very dated (McAllister, 2001) if it exists at all. The BBC produced two documentaries on dog inbreeding titled Pedigree Dogs Exposed and Pedigree Dogs Exposed: Three Years On that document
6461-463: The recessive allele is the result of a one-time mutation, or because white tigers lack adequate camouflage, reducing their ability to stalk prey or avoid other predators. A white tiger's pale coloration is due to the lack of the red and yellow pheomelanin pigments that normally produce the orange coloration. This had long been attributed to a mutation in the gene for the tyrosinase (TYR) enzyme. A knockout mutation in this gene results in albinism ,
6552-459: The relative proportion of homozygotes to heterozygotes; however, because the increased proportion of deleterious homozygotes exposes the allele to natural selection , in the long run its frequency decreases more rapidly in inbred populations. In the short term, incestuous reproduction is expected to increase the number of spontaneous abortions of zygotes, perinatal deaths, and postnatal offspring with birth defects. The advantages of inbreeding may be
6643-574: 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, and 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
6734-484: The right side. A male tiger named 'Cheytan', a son of Bhim and Sumita who was born at the Cincinnati Zoo, died at the San Antonio Zoo in 1992, from anaesthesia complications during root canal therapy . It appears that white tigers also react strangely to anaesthesia. The best drug for immobilizing a tiger is CI 744, but a few tigers, white ones in particular, undergo a re-sedation effect 24–36 hours later. This
6825-511: The same allele in an ancestor. These two identical alleles that are both derived from a common ancestor are said to be identical by descent . This probability F(A) is called the " coefficient of inbreeding ". Another useful measure that describes the extent to which two individuals are related (say individuals A and B) is their coancestry coefficient f(A,B), which gives the probability that one randomly selected allele from A and another randomly selected allele from B are identical by descent. This
6916-798: The same pattern. The stripes of the tiger are a pigmentation of the skin; if an individual were to be shaved, its distinctive coat pattern would still be visible. For a white Bengal tiger to be born, both parents must carry the unusual gene for white colouring, which only happens naturally about once in 10,000 births. Dark-striped white individuals are well-documented in the Bengal tiger subspecies ( Panthera tigris ) as well as having been reported historically in several other subspecies. Currently, several hundred white tigers are in captivity worldwide, with about one hundred being found in India. Their unique colouring has made them popular in entertainment showcasing exotic animals, and at zoos. Their rarity could be because
7007-490: The stock and for producing distinct families within a breed, but will need to watch for undesirable characteristics in offspring, which can then be eliminated through further selective breeding or culling . Inbreeding also helps to ascertain the type of gene action affecting a trait. Inbreeding is also used to reveal deleterious recessive alleles, which can then be eliminated through assortative breeding or through culling. In plant breeding , inbred lines are used as stocks for
7098-455: The takeover, allows the new selected gene complement of the incoming alpha male to prevail over the previous male. There are genetic assays being scheduled for lions to determine their genetic diversity. The preliminary studies show results inconsistent with the outcrossing paradigm based on individual environments of the studied groups. In Central California, sea otters were thought to have been driven to extinction due to over hunting, until
7189-507: The term is used in human reproduction , but more commonly refers to the genetic disorders and other consequences that may arise from expression of deleterious recessive traits resulting from incestuous sexual relationships and consanguinity . Animals avoid inbreeding only rarely. Inbreeding results in homozygosity which can increase the chances of offspring being affected by recessive traits . In extreme cases, this usually leads to at least temporarily decreased biological fitness of
7280-408: The trait carries throughout a population, all individuals can have this trait. This is called the founder effect . In the well established breeds, that are commonly bred, a large gene pool is present. For example, in 2004, over 18,000 Persian cats were registered. A possibility exists for a complete outcross, if no barriers exist between the individuals to breed. However, it is not always the case, and
7371-417: The traits themselves can cause problems, such as albinism's visual and neural effects. Additionally, animals with an abnormal appearance do not serve as well as ambassadors for their species in the zoos' mission to educate the public. Inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically . By analogy,
7462-425: The transfer of deleterious alleles may be achieved by reproductive isolation, sterilization , or, in the extreme case, culling . Culling is not strictly necessary if genetics are the only issue in hand. Small animals such as cats and dogs may be sterilized, but in the case of large agricultural animals, such as cattle, culling is usually the only economic option. The issue of casual breeders who inbreed irresponsibly
7553-468: The white Bengal tigers tend to grow faster and become heavier than the orange Bengal tiger. They also tend to be somewhat bigger at birth, and as fully grown adults. White Bengal tigers are fully grown when they are 2–3 years of age. White male tigers reach weights of 200 to 230 kilograms (440 to 510 lb) and can grow up to 3 meters (9.8 ft) in length. As with all tigers, the white Bengal tiger's stripes are like fingerprints, with no two tigers having
7644-513: The wrong side of the brain, white tigers have a problem with spatial orientation, and bump into things until they learn to compensate. Some tigers compensate by crossing their eyes. When the neurons pass from the retina to the brain and reach the optic chiasma, some cross and some do not, so that visual images are projected to the wrong hemisphere of the brain. White tigers cannot see as well as normal tigers and suffer from photophobia , like albinos. Other genetic problems include shortened tendons of
7735-439: The young of both sexes, thought to be a mechanism by which the species instinctively avoids some of the genetic consequences of inbreeding. In general, many mammal species, including humanity's closest primate relatives, avoid close inbreeding possibly due to the deleterious effects. Although there are several examples of inbred populations of wild animals, the negative consequences of this inbreeding are poorly documented. In
7826-444: Was Mohini's daughter Rewati. Strabismus is directly linked to the white gene and is not a separate consequence of inbreeding. The orange litter-mates of white tigers are not prone to strabismus. Siamese cats and albinos of every species which have been studied all exhibit the same visual pathway abnormality found in white tigers. Siamese cats are also sometimes cross-eyed, as are some albino ferrets . The visual pathway abnormality
7917-561: Was a 200 kg (450 lb) male cross-eyed white tiger at the Pana'ewa Rainforest Zoo in Hawaii , which was donated to the zoo by Las Vegas magician Dirk Arthur. There is a picture of a white tiger which appears to be cross-eyed on just one side in the book Siegfried and Roy: Mastering the Impossible . A white tiger, named Scarlett O'Hara, who was Tony's sister, was cross-eyed only on
8008-572: Was born in a wildlife refuge in Alicante , Spain. Its parents are normal orange Bengals. The cub was named "Artico" ("Arctic"). Outside of India, inbred white tigers have been prone to crossed eyes, a condition known as strabismus , due to incorrectly routed visual pathways in the brains of white tigers. When stressed or confused, all white tigers cross their eyes. Strabismus is associated with white tigers of mixed Bengal and Siberian ancestry. The only pure-Bengal white tiger reported to be cross-eyed
8099-504: Was bred to an unrelated orange tiger named Jack from the San Francisco Zoo and had an orange daughter named Kanchana. Bharat and Priya were also bred with an unrelated orange tiger from Knoxville Zoo , and Ranjit was bred to this tiger's sister, also from Knoxville Zoo. Bhim fathered several litters with an unrelated orange tigress named Kimanthi at the Cincinnati Zoo. The last descendants of Bristol Zoo 's white tigers were
8190-463: Was first documented in white tigers in the brain of a white tiger called Moni after he died, although his eyes were of normal alignment. The abnormality is that there is a disruption in the optic chiasm . The examination of Moni's brain suggested the disruption is less severe in white tigers than it is in Siamese cats. Because of the visual pathway abnormality, by which some optic nerves are routed to
8281-423: Was often practiced among European royal families, usually for interests of state. Over time, due to the relatively limited number of potential consorts, the gene pool of many ruling families grew progressively smaller, until all European royalty was related. This also resulted in many being descended from a certain person through many lines of descent, such as the numerous European royalty and nobility descended from
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