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81-451: Laboratory rats or lab rats are strains of the rat subspecies Rattus norvegicus domestica (Domestic Norwegian rat) which are bred and kept for scientific research . While less commonly used for research than laboratory mice , rats have served as an important animal model for research in psychology and biomedical science . In 18th-century Europe , wild brown rats ( Rattus norvegicus ) ran rampant and this infestation fueled

162-413: A chassis for the expression of simple proteins. These strains, such as BL21, are genetically modified to minimize protease activity, hence enabling potential for high efficiency industrial scale protein production . Strains of yeasts are the most common subjects of eukaryotic genetic modification, especially with respect to industrial fermentation . The term has no official ranking status in botany;

243-556: A dark brown, nearly black coat. They are more sensitive to noise and odours and are more likely to bite than the more docile laboratory strains such as BALB/c . Group-housed C57BL/6 mice (and other strains) display barbering behaviour, which used to be seen as a sign of dominance. However, it is now known that this is more of a stereotypical behaviour triggered by stress, comparable to trichotillomania in humans or feather plucking in parrots. Mice that have been barbered extensively can have large bald patches on their bodies, commonly around

324-456: A domesticated pet during the Edo period and in the 18th century guidebooks on keeping domestic rats were published by Youso Tamanokakehashi (1775) and Chingan Sodategusa (1787). Genetic analysis of 117 albino rat strains collected from all parts of the world carried out by a team led by Takashi Kuramoto at Kyoto University in 2012 showed that the albinos descended from hooded rats and all

405-447: A good model for early-stage AD because they show amyloidogenesis and working memory impairments linked to age but do not show neuronal degeneration. The absence of cell death suggests that changes in typical cellular signaling cascades involved in learning and synaptic plasticity are probably linked to the memory phenotype. Associative learning impairments are exacerbated when Tg2576 mice are crossed with PS1 transgenic animals that possess

486-450: A high (and very variable) rate, the study was considered flawed in design and its findings unsubstantiated. The biobreeding rat (a.k.a. the biobreeding diabetes-prone rat or BBDP rat) is an inbred strain that spontaneously develops autoimmune type 1 diabetes . Like NOD mice , biobreeding rats are used as an animal model for Type 1 diabetes. The strain re-capitulates many of the features of human type 1 diabetes and has contributed greatly to

567-463: A lower neutrophil enzymatic capacity, lower activity of the complement system , and a different set of pentraxins involved in the inflammatory process ; and lack genes for important components of the immune system, such as IL-8 , IL-37 , TLR10 , ICAM-3 , etc. Laboratory mice reared in specific-pathogen-free (SPF) conditions usually have a rather immature immune system with a deficit of memory T cells . These mice may have limited diversity of

648-644: A much higher rate compared to other strains, thus require less time for these behavioral studies. The Sprague Dawley is an outbred, multipurpose breed of albino rat used extensively in medical and nutritional research. Its main advantage is its calmness and ease of handling. This breed of rat was first produced by the Sprague Dawley farms (later to become the Sprague Dawley Animal Company ) in Madison, Wisconsin , in 1925. The name

729-405: A number of researchers. Regarding experiments on mice, some researchers have complained that "years and billions of dollars have been wasted following false leads" as a result of a preoccupation with the use of these animals in studies. Mice differ from humans in several immune properties: mice are more resistant to some toxins than humans; have a lower total neutrophil fraction in the blood ,

810-548: A population with genetic variation is required, and these rats are usually referred to as "stocks" rather than "strains". The Wistar rat is an outbred albino rat. This breed was developed at the Wistar Institute in 1906 for use in biological and medical research, and is notably the first rat developed to serve as a model organism at a time when laboratories primarily used the house mouse ( Mus musculus ). More than half of all laboratory rat strains are descended from

891-456: A rice plant, all the descendants of the genetically modified rice plant are a strain with unique genetic information that is passed on to later generations; the strain designation, which is normally a number or a formal name, covers all the plants that descend from the originally modified plant. The rice plants in the strain can be bred to other rice strains or cultivars , and if desirable plants are produced, these are further bred to stabilize

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972-535: A single breeding pair. Inbred mice have several traits that make them ideal for research purposes. They are isogenic , meaning that all animals are nearly genetically identical. Approximately 98.7% of the genetic loci in the genome are homozygous , so there are probably no "hidden" recessive traits that could cause problems. They also have very unified phenotypes due to this stability. Many inbred strains have well documented traits that make them ideal for specific types of research. The following table shows

1053-634: A standard for their care and use. Compliance with the PHS is required for a research project to receive federal funding. PHS policy is administered by the Office of Laboratory Animal Welfare. Many academic research institutes seek accreditation voluntarily, often through the Association for Assessment and Accreditation of Laboratory Animal Care , which maintains the standards of care found within The Guide for

1134-525: A tunnel or cupped hands is advocated. In behavioural tests, tail-handled mice show less willingness to explore and to investigate test stimuli, as opposed to tunnel-handled mice which readily explore and show robust responses to test stimuli. In nature, mice are usually herbivores , consuming a wide range of fruit or grain. However, in laboratory studies it is usually necessary to avoid biological variation and to achieve this, laboratory mice are almost always fed only commercial pelleted mouse feed. Food intake

1215-632: Is 20 days. A fertile postpartum estrus occurs 14–24 hours following parturition , and simultaneous lactation and gestation prolongs gestation by 3–10 days owing to delayed implantation. The average litter size is 10–12 during optimum production, but is highly strain-dependent. As a general rule, inbred mice tend to have longer gestation periods and smaller litters than outbred and hybrid mice. The young are called pups and weigh 0.5–1.5 g (0.018–0.053 oz) at birth, are hairless, and have closed eyelids and ears. Pups are weaned at 3 weeks of age when they weigh about 10–12 g (0.35–0.42 oz). If

1296-430: Is a group in which all members are as nearly as possible genetically identical. In laboratory mice, this is accomplished through inbreeding . By having this type of population, it is possible to conduct experiments on the roles of genes, or conduct experiments that exclude genetic variation as a factor. In contrast, outbred populations are used when identical genotypes are unnecessary or a population with genetic variation

1377-410: Is also possible. Each route has a recommended injection site, approximate needle gauge and recommended maximum injected volume at a single time at one site, as given in the table below: To facilitate intravenous injection into the tail, laboratory mice can be carefully warmed under heat lamps to vasodilate the vessels. A common regimen for general anesthesia for the house mouse is ketamine (in

1458-531: Is an albino laboratory-bred strain from which a number of common substrains are derived. With over 200 generations bred since 1920, BALB/c mice are distributed globally and are among the most widely used inbred strains used in animal experimentation . BALB/c are noted for displaying high levels of anxiety and for being relatively resistant to diet-induced atherosclerosis , making them a useful model for cardiovascular research. Male BALB/c mice are aggressive and will fight other males if housed together. However,

1539-465: Is approximately 15 g (0.53 oz) per 100 g (3.5 oz) of body weight per day; water intake is approximately 15 ml (0.53 imp fl oz; 0.51 US fl oz) per 100 g of body weight per day. Routes of administration of injections in laboratory mice are mainly subcutaneous , intraperitoneal and intravenous . Intramuscular administration is not recommended due to small muscle mass. Intracerebral administration

1620-437: Is considered genetically identical after 20 generations of sibling-mating. Many rodent strains have been developed for a variety of disease models, and they are also often used to test drug toxicity. The common fruit fly ( Drosophila melanogaster ) was among the first organisms used for genetic analysis , has a simple genome , and is very well understood. It has remained a popular model organism for many other reasons, like

1701-421: Is most common species for prokaryotic strain engineering. Scientists have succeeded in establishing viable minimal genomes from which new strains can be developed. These minimal strains provide a near guarantee that experiments on genes outside the minimal framework will not be effected by non-essential pathways. Optimized strains of E. coli are typically used for this application. E. coli are also often used as

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1782-582: Is no universally accepted definition for the terms 'strain', ' variant ', and 'isolate' in the virology community, and most virologists simply copy the usage of terms from others". A strain is a genetic variant or subtype of a microorganism (e.g., a virus , bacterium or fungus ). For example, a "flu strain" is a certain biological form of the influenza or "flu" virus. These flu strains are characterized by their differing isoforms of surface proteins. New viral strains can be created due to mutation or swapping of genetic components when two or more viruses infect

1863-781: Is reflected by the amount of literature on it: roughly 50% more than that on laboratory mice . Laboratory rats are frequently subject to dissection or microdialysis to study internal effects on organs and the brain, such as for cancer or pharmacological research. Laboratory rats not sacrificed may be euthanized or, in some cases, become pets . Domestic rats differ from wild rats (various spp. of Rodentia ) in many ways: they are calmer and significantly less likely to bite, they can tolerate greater crowding, they breed earlier and produce more offspring, and their brains , livers , kidneys , adrenal glands , and hearts are smaller. Scientists have bred many strains or "lines" of rats specifically for experimentation. Most are derived from

1944-608: Is required, and are usually referred to as stocks rather than strains . Over 400 standardized, inbred strains have been developed. Most laboratory mice are hybrids of different subspecies, most commonly of Mus musculus domesticus and Mus musculus musculus . Laboratory mice can have a variety of coat colours, including agouti, black and albino . Many (but not all) laboratory strains are inbred. The different strains are identified with specific letter-digit combinations; for example C57BL/6 and BALB/c . The first such inbred strains were produced in 1909 by Clarence Cook Little , who

2025-425: Is spontaneous. The duration of the estrous cycle is 4–5 days and lasts about 12 hours, occurring in the evening. Vaginal smears are useful in timed matings to determine the stage of the estrous cycle. Mating can be confirmed by the presence of a copulatory plug in the vagina up to 24 hours post-copulation. The presence of sperm on a vaginal smear is also a reliable indicator of mating. The average gestation period

2106-953: Is the Tg2576 strain of mice. The K670M and N671L double mutations seen in the human 695 splice-variant of the amyloid precursor protein (APP) are expressed by this strain. A hamster prion protein gene promoter , predominantly in neurons, drives the expression. When compared to non-transgenic littermates, Tg2576 mice show a five-fold rise in Aβ40 and a 10- to 15-fold increase in Aβ42/43. These mice develop senile plaques linked to cellular inflammatory responses because their brains have approximately five times as much transgenic mutant human APP than indigenous mouse APP. The mice exhibit main characteristics of Alzheimer's disease (AD), such as increased generation of amyloid fibrils with aging, plaque formation, and impaired hippocampus learning and memory. Tg2576 mice are

2187-485: Is the first known animal with inherited retinal degeneration. Although the genetic defect was not known for many years, it was identified in the year 2000 as a mutation in the gene MERTK. This mutation results in defective retinal pigment epithelium phagocytosis of photoreceptor outer segments. The shaking rat Kawasaki (SRK) is an autosomal recessive mutant that has a short deletion in the RELN (reelin) gene. This results in

2268-498: Is unusually sensitive to pain and to cold, and analgesic medications are less effective in this strain. Unlike most laboratory mouse strains, the C57BL/6 drinks alcoholic beverages voluntarily. It is more susceptible than average to morphine addiction , atherosclerosis , and age-related hearing loss . When compared directly to BALB/c mice, C57BL/6 mice also express both a robust response to social rewards and empathy. BALB/c

2349-681: The American Veterinary Medical Association issued new guidelines for CO 2 induction, stating that a flow rate of 10% to 30% volume/min is optimal for euthanasing laboratory mice. A recent study detected a murine astrovirus in laboratory mice held at more than half of the US and Japanese institutes investigated. Murine astrovirus was found in nine mice strains, including NSG , NOD-SCID , NSG-3GS , C57BL6 - Timp-3 , uPA-NOG , B6J , ICR, Bash2 , and BALB/C , with various degrees of prevalence. The pathogenicity of

2430-495: The H5N1 influenza virus. While funding for such research has aroused controversy at times due to safety concerns, leading to a temporary pause, it has subsequently proceeded. In biotechnology, microbial strains have been constructed to establish metabolic pathways suitable for treating a variety of applications. Historically, a major effort of metabolic research has been devoted to the field of biofuel production. Escherichia coli

2511-491: The Lewis are other well-known stocks developed from Wistars. The Long–Evans rat is an outbred rat developed by Long and Evans in 1915 by crossbreeding several Wistar females with a wild gray male. Long-Evans rats are white with a black hood, or occasionally white with a brown hood. They are utilized as a multipurpose model organism , frequently in behavioral research, especially in alcohol research. Long-Evans consume alcohol in

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2592-666: The National Institutes of Health (NIH) via the Rat Genome Sequencing Project Consortium , and work accomplished by the members of the Knock Out Rat Consortium (KORC). Knockout rat disease models for Parkinson's disease , Alzheimer's disease , hypertension , and diabetes , using zinc-finger nuclease technology, are being commercialized by SAGE Labs . Strain (biology) It has been said that "there

2673-408: The albino and hooded varieties. The first time one of these albino mutants was brought into a laboratory for a study was in 1828 for an experiment on fasting . Over the next 30 years, rats were used for several more experiments and eventually the laboratory rat became the first animal domesticated for purely scientific reasons. In Japan , there was a widespread practice of keeping rats as

2754-478: The microbiota , which directly affects the immune system and the development of pathological conditions. Moreover, persistent virus infections (for example, herpesviruses ) are activated in humans, but not in SPF mice with septic complications and may change the resistance to bacterial coinfections . "Dirty" mice are possibly better suitable for mimicking human pathologies. In addition, inbred mouse strains are used in

2835-691: The size and number of fat cells . Obesity in Zucker rats is primarily linked to their hyperphagic nature and excessive hunger; however, food intake does not fully explain the hyperlipidemia or overall body composition. A knockout rat (also spelled knock out or knock-out ) is a genetically engineered rat with a single gene turned off through a targeted mutation . Knockout rats can mimic human diseases, and are important tools for studying gene function and for drug discovery and development. The production of knockout rats became technically feasible in 2008, through work financed by $ 120 million in funding from

2916-622: The testicular tumors occurred in the rats from a single supplier. The researchers found that the incidence of tumors in Sprague Dawleys from different suppliers varied as much from each other as from the other strains of rats. The authors of the study "stressed the need for extreme caution in evaluation of carcinogenicity studies conducted at different laboratories and/or on rats from different sources." During food rationing due to World War II , British biologists had eaten laboratory rats, creamed. Scientists have also spent time studying

2997-426: The thermoregulation of the rat's tail in research. The rat's tail works as a variable heat exchanger. The tail's blood flow allows for thermoregulation to take place because it is under control of sympathetic vasoconstrictor nerves. Vasodilation occurs when the tail temperature increases, causing heat loss. Vasoconstriction occurs when the tail temperature decreases allowing heat to be conserved. Thermoregulation in

3078-544: The white-footed mouse ( Peromyscus leucopus ) and the North American deer mouse ( Peromyscus maniculatus ). Mice have been used in biomedical research since the 17th century when William Harvey used them for his studies on reproduction and blood circulation and Robert Hooke used them to investigate the biological consequences of an increase in air pressure. During the 18th century Joseph Priestley and Antoine Lavoisier both used mice to study respiration . In

3159-428: The 19th century Gregor Mendel carried out his early investigations of inheritance on mouse coat color but was asked by his superior to stop breeding in his cell "smelly creatures that, in addition, copulated and had sex". He then switched his investigations to peas but, as his observations were published in a somewhat obscure botanical journal, they were virtually ignored for over 35 years until they were rediscovered in

3240-662: The 20th and 21st Centuries. The Jackson Laboratory in Bar Harbor, Maine is currently one of the world's largest suppliers of laboratory mice, at around 3 million mice a year. The laboratory is also the world's source for more than 8,000 strains of genetically defined mice and is home of the Mouse Genome Informatics database. Breeding onset occurs at about 50 days of age in both females and males, although females may have their first estrus at 25–40 days. Mice are polyestrous and breed year round; ovulation

3321-507: The A246E FAD mutation. This crosses promotes the build-up of amyloid and plaque development in the CNS. This lends credence to the theory that AD pathogenesis is influenced by the interplay between APP and PS-1 gene products. Although Tg2576 mice do not perfectly replicate late-stage AD with cell death, they do offer a platform for researching the physiology and biochemistry of the illness.With

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3402-456: The BALB/Lac substrain is much more docile. Most BALB/c mice substrains have a long reproductive life-span. There are noted differences between different BALB/c substrains, though these are thought to be due to mutation rather than genetic contamination. The BALB/cWt is unusual in that 3% of progeny display true hermaphroditism . A useful model for Alzheimer's disease (AD) in the lab

3483-607: The Care and Use of Laboratory Animals and the PHS policy. This accreditation is, however, not a prerequisite for federal funding, unlike the actual compliance. While mice are by far the most widely used animals in biomedical research, recent studies have highlighted their limitations. For example, the utility of rodents in testing for sepsis , burns , inflammation , stroke , ALS , Alzheimer's disease , diabetes , cancer , multiple sclerosis , Parkinson's disease , and other illnesses has been called into question by

3564-674: The U.K. are published each year. In the U.K. in 2013, there were a total of 3,077,115 regulated procedures undertaken on mice in scientific procedure establishments, licensed under the Act. In the U.S., laboratory mice are not regulated under the Animal Welfare Act administered by the USDA APHIS . However, the Public Health Service Act (PHS) as administered by the National Institutes of Health does offer

3645-459: The ability to accurately extrapolate findings to humans. Researchers have also noted that many studies involving mice are poorly designed, leading to questionable findings. Some studies suggests that inadequate published data in animal testing may result in irreproducible research, with missing details about how experiments are done are omitted from published papers or differences in testing that may introduce bias. Examples of hidden bias include

3726-500: The albino Wistar rat , which is still widely used. Other common strains are the Sprague Dawley , Fischer 344 , Holtzman albino strains, Long–Evans , and Lister black hooded rats. Inbred strains are also available, but are not as commonly used as inbred mice. Much of the genome of Rattus norvegicus has been sequenced . In October 2003, researchers succeeded in cloning two laboratory rats by nuclear transfer . This

3807-556: The albinos descended from a single ancestor. As there is evidence that the hooded rat was known as the "Japanese rat" in the early 20th century, Kuramoto concluded that one or more Japanese hooded rats might have been brought to Europe or the Americas and an albino rat that emerged as a product of the breeding of these hooded rats was the common ancestor of all the albino laboratory rats in use today. The rat found early use in laboratory research in five areas: W. S. Small suggested that

3888-547: The closest non- primate relatives of humans along with lagomorphs , treeshrews , and flying lemurs . Rodentia (rodents) Lagomorpha (rabbits, hares, pikas) Scandentia (treeshrews) Dermoptera (flying lemurs) Primates († Plesiadapiformes , Strepsirrhini , Haplorrhini ) Laboratory mice are the same species as the house mouse ; however, they are often very different in behaviour and physiology . There are hundreds of established inbred , outbred , and transgenic strains. A strain , in reference to rodents,

3969-776: The design and execution of the tests themselves. In addition, the caging of laboratory animals may render them irrelevant models of human health because these animals lack day-to-day variations in experiences, agency, and challenges that they can overcome. The impoverished environments inside small mouse cages can have deleterious influences on biomedical results, especially with respect to studies of mental health and of systems that depend upon healthy psychological states. For example, researchers have found that many mice in laboratories are obese from excess food and minimal exercise, which alters their physiology and drug metabolism. Many laboratory animals, including mice, are chronically stressed, which can also negatively affect research outcomes and

4050-481: The desirable traits; the stabilized plants that can be propagated and "come true" (remain identical to the parent plant) are given a cultivar name and released into production to be used by farmers. A laboratory mouse or rat strain is a group of animals that is genetically uniform. Strains are used in laboratory experiments. Mouse strains can be inbred , mutated , or genetically modified , while rat strains are usually inbred . A given inbred rodent population

4131-425: The development of genetic research techniques applicable to rats. A 1972 study compared neoplasms in Sprague Dawleys from six different commercial suppliers and found highly significant differences in the incidences of endocrine and mammary tumors. There were even significant variations in the incidences of adrenal medulla tumors among rats from the same source raised in different laboratories. All but one of

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4212-438: The dose of 100 mg per kg body weight) plus xylazine (in the dose of 5–10 mg per kg), injected by the intraperitoneal route. It has a duration of effect of about 30 minutes. Approved procedures for euthanasia of laboratory mice include compressed CO 2 gas, injectable barbiturate anesthetics , inhalable anesthetics, such as Halothane, and physical methods, such as cervical dislocation and decapitation. In 2013,

4293-473: The early 1950s. Characteristics include albino coloring, docile behavior, and low fertility. The Lewis rat suffers from several spontaneous pathologies: first, they can suffer from high incidences of neoplasms, with the rat's lifespan mainly determined by this. The most common are adenomas of the pituitary and adenomas/adenocarcinomas of the adrenal cortex in both sexes, mammary gland tumors and endometrial carcinomas in females, and C-cell adenomas/adenocarcinomas of

4374-486: The early 20th century. In 1902 Lucien Cuénot published the results of his experiments using mice which showed that Mendel's laws of inheritance were also valid for animals — results that were soon confirmed and extended to other species. In the early part of the 20th century, Harvard undergraduate Clarence Cook Little was conducting studies on mouse genetics in the laboratory of William Ernest Castle . Little and Castle collaborated closely with Abbie Lathrop who

4455-488: The ease of its breeding and maintenance, and the speed and volume of its reproduction. Various specific strains have been developed, including a flightless version with stunted wings (also used in the pet trade as live food for small reptiles and amphibians). Laboratory mouse The laboratory mouse or lab mouse is a small mammal of the order Rodentia which is bred and used for scientific research or feeders for certain pets. Laboratory mice are usually of

4536-472: The female does not mate during the postpartum estrus, she resumes cycling 2–5 days post-weaning. Newborn males are distinguished from newborn females by noting the greater anogenital distance and larger genital papilla in the male. This is best accomplished by lifting the tails of littermates and comparing perinea . Mice are mammals of the clade (a group consisting of an ancestor and all its descendants) Euarchontoglires , which means they are amongst

4617-399: The head, snout, and shoulders, although barbering may appear anywhere on the body. Also self-barbering can occure. Both hair and vibrissae may be removed. Barbering is more frequently seen in female mice; male mice are more likely to display dominance through fighting. C57BL/6 has several unusual characteristics which make it useful for some research studies but inappropriate for others: It

4698-506: The help of transgenic mouse models, researchers can make progress in AD research by understanding the intricate relationships between gene products that are involved in the production of Aβ peptide.e physiology and biochemistry of the illness. Traditionally, laboratory mice have been picked up by the base of the tail. However, recent research has shown that this type of handling increases anxiety and aversive behaviour. Instead, handling mice using

4779-400: The industry of rat-catching. Rat-catchers would not only make money by trapping the rodents, but also by selling them for food or, more commonly, for rat-baiting . Rat-baiting was a popular sport, which involved filling a pit with rats and timing how long it took for a terrier to kill them all. Over time, breeding the rats for these contests may have produced variations in color, notably

4860-436: The litter of 17 drank and urinated excessively. Hairless laboratory rats provide researchers with valuable data regarding compromised immune systems and genetic kidney diseases. It is estimated that there are over 25 genes that cause recessive hairlessness in laboratory rats. The more common ones are denoted as rnu (Rowett nude), fz (fuzzy), and shn (shorn). The Lewis rat was developed by Margaret Lewis from Wistar stock in

4941-528: The lowered expression of reelin protein, essential for proper cortex lamination and cerebellum development. Its phenotype is similar to the widely researched reeler mouse. Shaking rat Kawasaki was first described in 1988. This and the Lewis rat are well-known stocks developed from Wistar rats. The Zucker rat was bred to be a genetic model for research on obesity and hypertension. They are named after Lois M. Zucker and Theodore F. Zucker, pioneer researchers in

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5022-399: The many available strains includes - Since 1998, it has been possible to clone mice from cells derived from adult animals. There are many strains of mice used in research, however, inbred strains are usually the animals of choice for most fields. Inbred mice are defined as being the product of at least 20 generations of brother X sister mating, with all individuals being derived from

5103-570: The murine astrovirus was not known. In the U.K., as with all other vertebrates and some invertebrates, any scientific procedure which is likely to cause "pain, suffering, distress or lasting harm" is regulated by the Home Office under the Animals (Scientific Procedures) Act 1986 . U.K. regulations are considered amongst the most comprehensive and rigorous in the world. Detailed data on the use of laboratory mice (and other species) in research in

5184-536: The original colony established by physiologist Henry Herbert Donaldson , scientific administrator Milton J. Greenman , and genetic researcher/embryologist Helen Dean King . The Wistar rat is currently one of the most popular rats used for laboratory research. It is characterized by its wide head, long ears, and a tail length that is always less than its body length. The Sprague Dawley and Long–Evans were developed from Wistars. Wistars are more active than others like Sprague Dawleys. The spontaneously hypertensive rat and

5265-514: The overwhelming majority of studies, while the human population is heterogeneous, pointing to the importance of studies in interstrain hybrid, outbred , and nonlinear mice. An article in The Scientist notes, "The difficulties associated with using animal models for human disease result from the metabolic, anatomic, and cellular differences between humans and other creatures, but the problems go even deeper than that" including issues with

5346-409: The physical and behavioural characteristics of house mice; however, due to many generations of artificial selection, some of these characteristics now vary markedly. Due to the large number of strains of laboratory mice, it is impractical to comprehensively describe the appearance and behaviour of all of them; however, they are described below for two of the most commonly used strains. C57BL/6 mice have

5427-483: The rat tail has been used to study metabolism. A " strain ", in reference to rodents, is a group in which all members are, as nearly as possible, genetically identical. In rats, this is accomplished through inbreeding . By having this kind of population, it is possible to conduct experiments on the roles of genes, or conduct experiments that exclude variations in genetics as a factor. By contrast, " outbred " populations are used when identical genotypes are unnecessary or

5508-541: The rate of learning could be measured by rats in a maze ; a suggestion employed by John B. Watson for his Ph.D. dissertation in 1903. The first rat colony in America used for nutrition research was started in January 1908 by Elmer McCollum and then, nutritive requirements of rats were used by Thomas Burr Osborne and Lafayette Mendel to determine the details of protein nutrition . The reproductive function of rats

5589-544: The research of T1DM pathogenesis. The Brattleboro rat is a strain that was developed by Henry A. Schroeder and technician Tim Vinton in West Brattleboro , Vermont, beginning in 1961, for Dartmouth Medical School . It has a naturally occurring genetic mutation that makes specimens unable to produce the hormone vasopressin , which helps control kidney function. The rats were being raised for laboratory use by Henry Schroeder and technician Tim Vinton, who noticed that

5670-404: The same cell in nature. These phenomena are known respectively as antigenic drift and antigenic shift . Microbial strains can also be differentiated by their genetic makeup using metagenomic methods to maximize resolution within species. This has become a valuable tool to analyze the microbiome . Scientists have modified strains of viruses in order to study their behavior, as in the case of

5751-408: The size of the human genome. Estimating the number of genes contained in the mouse genome is difficult, in part because the definition of a gene is still being debated and extended. The current count of primary coding genes in the laboratory mouse is 23,139. compared to an estimated 20,774 in humans. Various mutant strains of mice have been created by a number of methods. A small selection from

5832-820: The species Mus musculus . They are the most commonly used mammalian research model and are used for research in genetics , physiology , psychology , medicine and other scientific disciplines . Mice belong to the Euarchontoglires clade, which includes humans . This close relationship, the associated high homology with humans, their ease of maintenance and handling, and their high reproduction rate, make mice particularly suitable models for human-oriented research. The laboratory mouse genome has been sequenced and many mouse genes have human homologues. Lab mice are sold at pet stores for snake food and can also be kept as pets . Other mouse species sometimes used in laboratory research include two American species,

5913-588: The study of the genetics of obesity. There are two types of Zucker rat: a lean Zucker rat, denoted as the dominant trait (Fa/Fa) or (Fa/fa); and the characteristically obese (or fatty) Zucker rat or Zucker diabetic fatty rat (ZDF rat), which is actually a recessive trait (fa/fa) of the leptin receptor , capable of weighing up to 1 kilogram (2.2 lb) — more than twice the average weight. Obese Zucker rats have high levels of lipids and cholesterol in their bloodstream, are resistant to insulin without being hyperglycemic , and gain weight from an increase in both

5994-427: The term refers to the collective descendants produced from a common ancestor that share a uniform morphological or physiological character. A strain is a designated group of offspring that are either descended from a modified plant (produced by conventional breeding or by biotechnological means), or which result from genetic mutation. As an example, some rice strains are made by inserting new genetic material into

6075-450: The thyroid gland and tumors of the hematopoietic system in males. Second, Lewis rats are prone to develop a spontaneous transplantable lymphatic leukaemia. Lastly, when in advanced age, they sometimes develop spontaneous glomerular sclerosis. Research applications include transplantation research, induced arthritis and inflammation, experimental allergic encephalitis, and STZ-induced diabetes. The Royal College of Surgeons rat (or RCS rat)

6156-640: The top 10 most popular strains according to Jackson Laboratories . The Jackson Labs DO ( Diversity Outbred ) project is a mouse breeding program using multiple inbred founder strains to create a genetically diverse population of mice for use in scientific research. These mice are designed for fine genetic mapping , and capture a large portion of the genetic diversity of the mouse genome. This project has resulted in over 1,000 genetically diverse mice which have been used to identify genetic factors for diseases such as obesity, cancer, diabetes, and alcohol use disorder. Laboratory mice have retained many of

6237-495: Was a breeder of fancy mice and rats which she marketed to rodent hobbyists and keepers of exotic pets, and later began selling in large numbers to scientific researchers. Together they generated the DBA (Dilute, Brown and non-Agouti) inbred mouse strain and initiated the systematic generation of inbred strains. The mouse has since been used extensively as a model organism and is associated with many important biological discoveries of

6318-512: Was influential in promoting the mouse as a laboratory organism. In 2011, an estimated 83% of laboratory rodents supplied in the U.S. were C57BL/6 laboratory mice. Sequencing of the laboratory mouse genome was completed in late 2002 using the C57BL/6 strain. This was only the second mammalian genome to be sequenced after humans. The haploid genome is about three billion base pairs long (3,000 Mb distributed over 19 autosomal chromosomes plus 1 respectively 2 sex chromosomes), therefore equal to

6399-509: Was originally hyphenated, although the brand styling today (Sprague Dawley, the trademark used by Inotiv ) is not. The average litter size of the Sprague Dawley rat is 11.0. These rats typically have a longer tail in proportion to their body length than Wistars. They were used in the Séralini affair , where the herbicide RoundUp was claimed to increase the occurrence of tumor in these rats. However, since these rats are known to grow tumors at

6480-704: Was studied at the Institute for Experimental Biology at the University of California, Berkeley by Herbert McLean Evans and Joseph A. Long. The genetics of rats was studied by William Ernest Castle at the Bussey Institute of Harvard University until it closed in 1994. Rats have long been used in cancer research ; for instance at the Crocker Institute for Cancer Research . The historical importance of this species to scientific research

6561-477: Was the first in a series of developments that have begun to make rats tractable as genetic research subjects, although they still lag behind mice, which lend themselves better to the embryonic stem cell techniques typically used for genetic manipulation . Many investigators who wish to trace observations on behavior and physiology to underlying genes regard aspects of these in rats as more relevant to humans and easier to observe than in mice, giving impetus to

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