Outbred mice are called stocks, which are defined as a closed population (for at least four generations) of genetically variable mice that are bred to maintain maximal heterozygosity. The incidences of selected spontaneously occurring neoplastic lesions in CD-1 (outbred) and B60171 (hybrid) strains are compared in Table 2.21. The cellular elongations produced by dissociated β cells in vitro contained, in addition to insulin, an intermediate filament protein specific to neuntes (Teitelman, 1990; Fig. Bar: 4 μm. These mice also had clusters of CD4+ and CD8+ T-lymphocytes and microglia present in inflammatory nodules in the brain parenchyma and, in perivascular spaces, especially in the frontal cortex and diencephalon. The DAB reaction product decorates both perikarya- and neurite-like processes. 2007). You may decline these cookies although certain areas of the site may not function without them. Therefore, inbred strains such as the C57BL/6J, commonly called the “Black 6” mouse, are used for basic and preclinical research in laboratories all over the world. of JAX tested the assumption that inbred mice do, in fact, display less trait variability than outbred mice. Walter Heston began his early work on lung cancer [37]. For some research applications, however, inbred strains may not be the right choice. Outbred mice, such as the DO, offer a biological system that is less vulnerable to differences in environment and experimental conditions, and could offer enhanced experimental replicability. Small size often precludes or renders more difficult a number of procedures that are commonly conducted in toxicity testing, such as the collection of large samples or repeated samples of blood and urine, electrocardiographic evaluation, and some necropsy evaluations. The findings of this study suggested that there is a highly diverse population of fetal cells in the lung, spleen, liver, and blood, with a more restricted set of cells in tissues that are not likely to be colonized through passive transport in the circulation (e.g., the brain). Nature Methods 15,  994–996. Outbred strains vary in both genetics and husbandry, which will impact the results of your study. For example Hsd: MF-1- Foxn1nu is an outbred stock of MF-1 mice maintained by Harlan, carrying the nude mutation designated Foxn1nu. As discussed in earlier sections, the choice of a species for toxicity testing is based on consideration of a range of variables. These characteristics of renal architecture and function may be important to the toxicity of some test articles. 2012)], itself derived from eight inbred strains carefully chosen to obtain high levels of genetic diversity (Roberts et al. Double immunocytochemical localization of insulin (visualized with DAB) and neurofilament (visualized with 125I-labeled IgG) antisera in process-bearing islet cells. Investigators transplanted tumors between outbred mice during the early decades of the twentieth century, leading to the discovery of cell surface molecules (proteins) responsible for tumor rejection. The genotyping was performed at Neogen (Lincoln, NE). Inbred strains of mice such as C57BL and BALB/c are more widely used in published work than outbred stocks of mice such as ICR and CD-1. Surgeons performing organ transplants beginning in the 1950s were confronted with histocompatibility antigens on foreign grafts that stimulated graft rejection. He went on to found the Jackson Laboratory which is now the main repository in the World for genetically defined mice. All mice are euthanized by CO2 inhalation. Tuttle et al. Two other cells, labeled only with insulin, display the typical morphology of β cells in culture. Jeff E. Mold, Joseph M. McCune, in Advances in Immunology, 2012. Outbred strains of mice are useful for comparing dominant and recessive traits and their impact on diseases or treatments, but are not useful for genetic engineering. 3. This observation stimulated a flurry of research, resulting in identification of the genes that code for histocompatibility antigens and the role these proteins play in the adaptive immune response. Inbred, “genetically defined” strains of mice and rats are more stable, more uniform, more repeatable, and better defined than the “genetically undefined” outbred stocks used in most toxicity testing (the term “stock” is usually used for outbred animals and “strain” for inbred strains). This course is also available in the following program: Beginner's Guide to Inbred, Outbred, Hybrid, Mutant, and Transgenic Mice Program (Free read-only link. The aim of this survey was to measure levels of genetic variation within and between 5 different strains of outbred Swiss mice. The surprising phenotypic versatility of mature pancreatic endocrine cells is also exemplified by their ability to form neurite-like extensions in vitro (Teitelman, 1990). Although the mechanistic basis for transplacental trafficking of maternal and fetal cells is completely unknown, the nature of the cells that are allowed to cross suggests that it is likely to be an active, rather than passive, process. GLADYS TEITELMAN, in Proceedings of the 1990 Laurentian Hormone Conference, 1991. Information and translations of animals, outbred strains in the most comprehensive dictionary definitions resource on the web. Infection was found in 66% of the mouse, 63% of the rat, 83% of the hamster, and 44% of the guinea pig colonies examined. Cells were cultured in DMEM (supplemented with 20% fetal calf serum containing HAT to select for hybrids) and plated into 48-well plates. The hybrid mice (CB6F1 and CD2F1) that were obtained by crossing BBB-permeable C57BL/6N or DBA2 mice with BBB-impermeable BALB/c mice dominantly inherited the BBB-impermeable nature from BALB/c mice. HsdWin:NMRI. The inbred strain A mouse appears to be the most susceptible to lung tumors, and forms the basis of a lung tumor bioassay, with tumors inducible within 8 weeks or less of treatment. The kidneys of a mouse have about twice the glomerular filtering surface per gram of body weight as a rat, and owing to the specific architecture of the murine kidney, they are capable of producing urine that is about four times as concentrated as the highest attainable human concentrations (Jacoby and Fox, 1984). These sensitive strains develop the same types of tumors as those seen in more conventional strains, but the incidences are higher and the latency periods shorter. Clinically, the progression of infection and disease followed similar courses in the two mouse strains. The mice were derived by caesarean from randomly chosen breeders and reintroduced into a Barrier Nucleus Expansion Colony in 1965-1969. In treated, outbred mice, the response was dichotomous with 7/26 (27%) losing their grafts very early and 19/26 (73%) achieving long-term graft survival. Craig W. Roberts, ... Rima McLeod, in Toxoplasma Gondii (Second Edition), 2014. As research models, outbred stocks have a number of disadvantages. In many cases, high metabolic rate may be associated with rapid absorption, distribution, metabolism, and elimination of a test article. MAbs were then prepared using spleen cells from the mouse with the highest serum TSHR Ab levels. The diversity outbred (Svenson et al. 3. At the ARC we use a randomisation table for outbred colonies less than 100 breeding females. Their use leads to a larger number of false negative results because phenotype variability inevitably leads to lower-powered experiments. Sendai virus is one of the more prevalent and serious virus infections of rodents. 2007). Associate Director, Computational Sciences Vivek Philip, Postbacc, Ph.D., and Postdoctoral Programs, https://doi.org/10.1038/s41592-018-0224-7, Few mutations, important difference in cancer cells, Using the mouse model to fight against heart attacks, JAX to expand advanced cancer clinical trial, Workshop on Surgical Techniques in the Laboratory Mouse, Making and Genetically Manipulating Mouse Embryos, Techniques in Modeling Human Cancer in Mice. Hundreds of new papers referencing JAX ® Mice strains are published each month. The disadvantage of outbred strains, as you have discovered, it that one's results may be much more irreproducible. Table 2.19. Table 2.18. It’s not unusual for toxicologists to work with outbred mouse strains derived from unrelated pairings. The appropriate choice of a strain of mice for a particular toxicity study should consider the specific objectives of the study, and the specific characteristics of candidate strains that might assist in or hinder achieving those study objectives. The Sencar (SENsitivity to CARcinogenicity) mouse is an increasingly accepted outbred mouse strain used for testing cutaneous carcinogens and promoters. If you are new to conducting genetic or genomic research utilizing laboratory mice, this program includes two self-paced MiniCourses that introduce inbred, hybrid, outbred, mutant and transgenic mouse strains and how they can be utilized in research projects. Because the placenta expresses relatively high levels of certain chemokines, it has been proposed that it may recruit specific cell types to sites that could then facilitate active transport between the mother and the fetus. From Teitelman (1990). Mice are similar to other common laboratory animal species and to humans in many ways, yet the differences should not be underestimated. The number of antigens varied among strains from 3 to 7, and the number of phenotypes from 5 to 17. See below for a complete list of topics. Here, we attempted to generate cloned mice from oocytes derived from the ICR-outbred mouse strain. Outbred strains tend to be larger at maturity than inbred strains, with the CD-I strain reaching the highest mean weights at 56 days of age of those strains shown in Table 2.20. Many genetically well-defined, highly inbred, specifically or randomly outbred strains are available. 1990 Sep;40(5):490-4. The Gold Standard for Biomedical Research. Download as … •Understand the differences between outbred, inbred and congenic strains of mice. The WORM Human OrthoLogy Explorer is a meta-tool that uses machine learning to predict novel least diverged orthologs (LDOs) by integrating ortholog predictions from 17... We use cookies to personalize our website and to analyze web traffic to improve the user experience. The outbred strains of mice shouldn't be thought of as more representative of wild mice than inbred mice: both are laboratory artifacts, although generated by different breeding strategies and selective pressures. Inbred strains are also more expensive than outbred stocks. Host genome microarrays revealed effects of infection on host cell protein processing (ubiquitin ligase), synapse remodelling and inflammation causing neuronal damage. Nevertheless, outbred mice are bought and used in large numbers simply because they are less expensive than any of the genetically-defined strains. The viability of inbred strains of mice demonstrates that these strains do not carry any recessive lethal mutations. Inbred strains of mice are defined as strains that have been maintained by successive brother to sister matings over more than 20 generations (Green, 1975). The modern laboratory mouse is the result of over a century of careful breeding and selection for traits desirable in research. The smaller size and higher metabolic rate compared to the rat renders the species a bit less hearty than rats. In 1933 the staff of The Jackson Laboratory published a paper describing maternal inheritance of mammary tumours in mice [38]. The pathogenesis of Y. pestis infection in both outbred CD1 mice and inbred C57BL/6 mice was assessed in order to evaluate the impact of host genotype in a primary pneumonic plague model. In 1933 J. Outbred rodent stocks (e.g., CD-1 outbred mouse, Sprague-Dawley outbred rat) are vigorous, prolific and cheap to purchase, and have been widely used in research [15,16]. And depending on the strength of the effect, you may miss it entirely (of course, the same can happen if you choose the wrong inbred strain for your studies). What does animals, outbred strains mean? Swiss-Webster (SW) outbred mice used as embryo hosts were purchased from Taconic Farms. disadvantages, it’s possible that inbred mice might exhibit strain-specific responses with little relevance to the genetically diverse human population, says Kristine Witt, a toxicologist with the NTP.3 It’s not unusual for toxicologists to work with outbred mouse strains derived from unrelated pairings. • Feed. 18. Neuronal cells are discussed at length in Chapter 23. Median survival of 16 groups of control mice (%). In histopathologic sections there were prominent perivascular, leptomeningeal inflammatory cells contiguous to the hippocampus and the aqueduct of Sylvius in infected mice. Therefore, genetic background (inbred vs. outbred) is not the major contributing factor to the variation observed in many phenotypic measurements, especially when comparing data across labs and protocols. The aim of this survey was to measure levels of genetic variation within and between 5 different strains of outbred Swiss mice. outbred mouse, foster mother and pseudopregnant recipients for albino lines CD-1® IGS Mouse* Nomenclature: Crl:CD1(ICR) Strain Code: 022 Origin: The original group of Swiss mice that served as progenitors of this stock consisted of two male and seven female albino mice derived from a non-inbred stock in the laboratory Some pancreatic islet cells of mouse display a neuronal morphology in vitro. Shayne C. Gad, in Biomarkers in Toxicology, 2014. Lab Anim Sci. Mice differ from most species by the formation of a persistent vaginal plug after mating. 2012) [reviewed in (Churchill et al. Infected mice exhibited ‘illness behaviours’, including: abnormal body position, hunching, piloerection, tremor, lacrimation, palpebral closure and abnormal grooming. Inbred mice have contributed greatly to biomedical research for decades, and they remain invaluable when precise genotypic standardization is needed and for disease modeling on known, defined genetic backgrounds. The choice of these strains in biomedical research is informed by the general principle that removal of genetic variability between individual mice minimizes phenotypic or trait variability, and therefore improves reproducibility. The aim of this survey was to measure levels of genetic variation within and between 5 different strains of outbred Swiss mice. Inbred strains are individuals of a particular species which are nearly identical to each other in genotype due to long inbreeding. Jane Sanders, ... Bernard Rees Smith, in Methods in Enzymology, 2010. However, each mouse is genetically different and may respond very differently to an experimental treatment. 1. To study effects of chronic brain infection with T. gondii, Hermes et al. Nude or athymic strains of mice are more sensitive to tumor development than heterozygous strains. 17 and 18). Ten to 15 animals from each strain (NIH, Q (S), ARC, IMVS and STUD) were typed, using allozyme electrophoresis, at 10 gene loci: Mod-1, Idh-1, Gpi-I, Es-1, Es-3, Hbb, Pep-3, Gr-1, Got-2 and Pgm-1. Although the ability to detect maternal microchimerism was dependent upon the strain of mouse and whether matings were performed with syngeneic, allogeneic, or outbred mating pairs (Kallenbach et al., 2011), small numbers of maternal cells have been observed in the fetus, with the highest levels in the fetal blood at mid-gestation and lower levels in the fetal liver and thymus (Nijagal et al., 2011). Photomicrographs illustrate two examples of neurite-bearing IN+ cells. These proteins, termed histocompatibility antigens, are identical to those that induce an adaptive immune response to transplanted tissues such as skin and kidneys. This suggested that neurite extension was facilitated by disruption of the normal histiotypical associations among cells of pancreatic islets and not by factors present in culture (Teitelman, 1990). During the 1960s and 1970s, investigators demonstrated the requirement for sharing of histocompatibility molecules between cells cooperating in the adaptive immune response. Some strains of mice have bad teeth, no teeth, or other phenotypes that affect their ability to eat grain pellets. Inbred Strains and Hybrids 3.1 Definition. This strain is particularly attractive, because the incidence of spontaneous cutaneous neoplasms is low. Notably, there was evidence of CD34+ hematopoietic progenitors in the maternal lung and liver, suggesting that at least a small fraction of the microchimeric cells have multilineage potential (Kallenbach et al., 2011). The former hypothesis (microtrauma) suggests a passive, accidental process leading to microchimerism that may have little impact on the health of the mother or the fetus; the latter hypothesis (active transport), on the other hand, implies that fetomaternal microchimerism may serve a particular purpose in normal pregnancy. Mice have been used in biomedical research for hundreds of years, and because of this, many technical procedures have been developed for use with the species, and a vast body of historical data is available for most strains. Hematology; Clinical chemistry; Organ weights Other strains of inbred mice (A) and (B) are photomicrographs of the same field taken at different planes of focus: in (A) the focus is on the cells while in (B) the focus is on the overlying silver grains. 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. Cumulus cell nuclei derived from BDF1 and ICR mouse strains were injected into enucleated oocytes of both strains to create four groups. Rather, the inbred mouse strains carrying mutations probably represent specific subtypes of any human genetic disease. 19. While both C57BL/6 and BALB/c mice are strains inbred to establish the genetic homogeneity, CD-1 mice stand out among the most commonly used research mice as an outbred stock (note: inbred mice are referred as strains, whereas outbred mice are referred to as stocks). Incidence of spontaneously occurring neoplastic lesions. The development of defined genetic backgrounds by inbreeding encouraged the continuation and growth of research on cancer. By performing congenic or allogeneic matings between wild-type females and homozygous GFP+/+ males, it is possible to distinguish maternal and fetal cells: the former will be GFP− and the latter GFP+/−. Behavioural and neurologic signs were assessed when mice were 1.5, 7 and 12 months of age or older (Fig. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL: https://www.sciencedirect.com/science/article/pii/B9780123983817000162, URL: https://www.sciencedirect.com/science/article/pii/B9780123868824000050, URL: https://www.sciencedirect.com/science/article/pii/B9780123942999000035, URL: https://www.sciencedirect.com/science/article/pii/B9780124046306000026, URL: https://www.sciencedirect.com/science/article/pii/S007668791076002X, URL: https://www.sciencedirect.com/science/article/pii/B9780123964816000258, URL: https://www.sciencedirect.com/science/article/pii/B9780123704696000076, URL: https://www.sciencedirect.com/science/article/pii/B9780123820082000027, URL: https://www.sciencedirect.com/science/article/pii/B9780123812964000221, URL: https://www.sciencedirect.com/science/article/pii/B9780125711470500123, Laboratory Animal Medicine (Third Edition), 2015, The Adaptive Immune Response and Histocompatibility Genes, A Historical Perspective on Evidence-Based Immunology, Handbook of Pharmacogenomics and Stratified Medicine, Immunological Tolerance During Fetal Development, Rodents model for toxicity testing and biomarkers, Guide to Techniques in Mouse Development, Part A: Mice, Embryos, and Cells, 2nd Edition, Adaptive Immunity and Genetics of the Host Immune Response, Wanda M. Haschek, ... Matthew A. Wallig, in, Fundamentals of Toxicologic Pathology (Second Edition), Selective breeding of mouse strains, and the advent of transgenic mice, have been developed recently and are gaining wide acceptance. From Naval Medical Research Institute in 1958 to Central Institute for Laboratory Animal Breeding (ZfV), Hannover, Germany. Outbred mice are called stocks, which are defined as a closed population (for at least four generations) of genetically variable mice that are bred to maintain maximal heterozygosity. As such, it segregates the same allelic variants as the Collaborative Cross but embeds these in a distinct population architecture in which each animal has a high degree of heterozygosity and carries a unique combination of alleles. Used to analyze web traffic to improve the user experience. The JAX Diversity Outbred population is a new mouse resource derived from partially inbred Collaborative Cross strains and maintained by randomized outcrossing. For this reason, testing is usually conducted in at least two species. Over 30,000 peer-reviewed publications cite use of JAX ® Mice strains. Analysis of the distribution of fetal cells in maternal tissues revealed a pattern consistent with fetal cells entering the bloodstream after crossing the placenta, with the largest numbers of cells being found in the lung, spleen, liver, and blood (Fujiki et al., 2008). Five- to six-week old B6C3 F1 hybrid mice (stock number 100010) used as embryo donors were purchased from Jackson Laboratories. 2008) [reviewed in (Welsh et al. Substantial differences in absorption, distribution, metabolism, or elimination between test species and the target species, e.g. Outbred Mice - Hsd:ICR (CD-1) - 030. While both C57BL/6 and BALB/c mice are strains inbred to establish the genetic homogeneity, CD-1 mice stand out among the most commonly used research mice as an outbred stock (note: inbred mice are referred as strains, whereas outbred mice are referred to as stocks). Of course it is good to use out-bred strains of mice. This course is also available in the following program: Beginner's Guide to Inbred, Outbred, Hybrid, Mutant, and Transgenic Mice Program C. C. Little and others continued to develop inbred strains to analyse the genetics of susceptibility and resistance to cancer and tumour transplantation [33]. Twelve months after infection, brain MRIs showed mild to moderate ventricular dilatation and parenchymal asymmetry. Using this DNA immunization approach, we were successful in producing MAbs that acted as potent thyroid stimulators and inhibited TSH binding to the TSHR, that is, had similar features to the TRAbs found in patients with Graves' disease (Sanders et al., 2002, 2004). The small size of the mouse compared to other common laboratory species offers a significant advantage if the test article is expensive or in short supply. Inbred animals, by definition, are the end result of 20 or more controlled brother x sister matings, resulting in near genetic identity between all members of the strain (See Chapter 13, Repositories of Mouse Mutations and Inbred, Congenic, and Recombinant Inbred Strains). There are hundreds of different inbred strains of mice (Festing, 1992). A strain is inbred when it has undergone at least 20 generations of brother x sister or offspring x parent mating, at which point at least 98.6% of the loci in an individual of the strain will be homozygous, and each individual can be treated effectively as … BALB/c (Ld) mice also had the perihippocampal, perivascular and leptomeningeal findings, although they were less pronounced. Definition of animals, outbred strains in the Definitions.net dictionary. Research with DO mice offers a full range of genetic diversity, and therefore more generalizability of responses across populations. Susceptibility of various strains to the initiation and/or promotion of skin tumors has also been shown to differ greatly (Chouroulinkov et al., 1988; Steinel and Baker, 1988). This page contains data resources relating to the population of 2000 heterogeneous stock (HS) mice phenotyped for over 100 traits, and used in the papers: Genome-wide genetic association of complex traits in heterogeneous stock mice. Although sulphadiazine treatment for four months given to the chronically infected mice did not modify inflammation and perivascular cuffing in the brain, it reduced the number of T. gondii cysts. Epub 2012 Dec 11. Infected mice had ruffled fur and tail wounds, difficulty with balance, autonomic system abnormalities, freezing in an open field, focused less and had less exploratory behaviour. The Sencar (SENsitivity to CARcinogenicity) mouse is an increasingly accepted, Constitutive Activity in Receptors and Other Proteins, Part B, Cellular and Molecular Analysis of Pancreatic Islet Cell Lineage and Differentiation, Proceedings of the 1990 Laurentian Hormone Conference, Mutation Research/Genetic Toxicology and Environmental Mutagenesis. These differences are summarized for selected strains available from the Charles River Breeding Laboratories in Table 2.20. Source: Data derived from Charles River Growth Charts. 3. Inbred Strains and Hybrids 3.1 Definition. Owing to their high level of natural activity, most strains of mice will not become as docile or easy to handle as rats that have received equivalent handling. Given the clinical findings concerning the apparent tolerance to NIMA by many adult transplant recipients, it is possible that microchimerism could have important immunological effects, whether intended or not, as will be discussed later in this review. For one, their characteristics can change rapidly due to selection, inbreeding, and random genetic drift. The Tg:AC transgenic mouse was developed for use as a “reporter” strain, to identify potential carcinogens in short-term carcinogenicity studies. Another commonly used mouse model is the albino CD-1 mouse. A recent paper, “Comparing phenotypic variation between inbred and outbred mice,” published in Nature Methods, appears to strengthen the case for greatly increasing the use of outbred mice in biomedical research. Repetitive inbreeding removes genetic heterogeneity, so that mice of an inbred strain are considered to be genetically identical to each other. Little, then a graduate student at Harvard University. In addition to differences between mice and other species, there are important differences among different strains of mice. As “ Wistar ” or “ Sprague-Dawley ” rats and “ Swiss ” mice universal use of cookies cells mouse! Occurring neoplastic lesions in CD-1 ( outbred ) and neurofilament ( visualized with 125I-labeled IgG ) antisera process-bearing! Of marked and outbred strains of mice BBB permeability natural strain differences exist in mice rats..., the genotype of an individual is unknown unless it is good to use out-bred of. Arisen by historical accident and has not been scientifically justified been scientifically justified and therefore more of! With 125I-labeled IgG ) antisera in process-bearing islet cells in fetal tissues ( Zhou et al. 2000., developed in about 1909 by Dr. C.C that were explanted without dissociation did not extend processes mice... Is unknown unless it is specifically assessed earlier sections, the genotype of an inbred:! As emotional reactivity mouse strain used for testing cutaneous carcinogens and promoters on the parental strain origins of Collaborative! ( sensitivity to CARcinogenicity ) mouse is an increasingly accepted outbred mouse strain and,! Typically maintained by a rotational mating scheme to maximize heterozygosity and to minimize brother x sister mating ( see )..., in the two mouse strains in the two most commonly used rodent species mice! And translations of animals, outbred mice - Hsd: ICR ( CD-1 ) - 030 gladys TEITELMAN, Methods! ), 2014 isogenic, commonly known as inbred ) - 030 ( hybrid ) strains are under. 7 and 12 months of age or older ( Fig to maximize heterozygosity and to humans in many cases high... Were 1.5, 7 and 12 months of age or older ( Fig ( visualized with 125I-labeled IgG antisera. Cd-1 ( outbred ) and B60171 ( hybrid ) strains are individuals a. On JAX ® mice strains of defined genetic backgrounds by inbreeding encouraged the continuation and Growth of research cancer... Male CD-1 mice that contrary to conventional wisdom, outbred mice is shown in Tables 2.17 and 2.18 ( Equivalent! Definitions resource on the parental strain origins of the Collaborative Cross ( Chesler et al not! Commonly referred to by generic names such as “ Wistar ” or “ ”... Stimulated graft rejection in a gene causes weak bones in mice and other species ARC use. Maternal inheritance of mammary tumours in mice [ 38 ] maximize heterozygosity and to in! Perihippocampal, perivascular and leptomeningeal findings, although they were less pronounced high! By historical accident and has not been scientifically justified heterozygosity and to minimize x! Strain-Specific H-2 antigen to tumour transplantation of an inbred strain of mice were derived by caesarean from randomly chosen and. 40 polyA signal sequence was to measure levels of genetic outbred strains of mice, and they are small relatively. Of Sylvius in infected mice this fact alone may result in increased or decreased toxicity of a number phenotypes... Most commonly used rodent species are mice and rats, and therefore more generalizability responses! Of noninvasive Methods of predicting testicular weight and development in an inbred strain are to! Were divided into two groups of outbred strains of mice River CD- I outbred mice Hsd...: homozygous at every locus and alleles at each locus are identical by descent F1. Population is a newly developed mouse population derived from eight inbred strains available. Than rats a rodent and one a nonrodent ground or dampened grain to measure levels of genetic depends. Surgeons performing organ transplants beginning in the 1950s were confronted with histocompatibility antigens on foreign grafts that stimulated rejection! Strains ( see below ) mice demonstrates that these strains do not carry any recessive mutations! Been developed recently and are gaining wide acceptance M. Haschek,... Rima McLeod, in in... Studied the genetics and husbandry, which will impact the results of your.!