Portal:Model organisms
Portal maintenance status: (October 2018)
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Introduction
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to research human disease when human experimentation would be unfeasible or unethical. This strategy is made possible by the common descent of all living organisms, and the conservation of metabolic and developmental pathways and genetic material over the course of evolution.[page needed]
Studying model organisms can be informative, but care must be taken when extrapolating from one organism to another.[page needed]
Selected major model organisms
Schizosaccharomyces pombe, also called "fission yeast", is a species of yeast used in traditional brewing and as a model organism in molecular and cell biology. It is a unicellular eukaryote, whose cells are rod-shaped. Cells typically measure 3 to 4 micrometres in diameter and 7 to 14 micrometres in length. Its genome, which is approximately 14.1 million base pairs, is estimated to contain 4,970 protein-coding genes and at least 450 non-coding RNAs.
These cells maintain their shape by growing exclusively through the cell tips and divide by medial fission to produce two daughter cells of equal size, which makes them a powerful tool in cell cycle research. Read more...
E. coli colonies containing the fluorescent pGLO plasmid
Escherichia coli (/ˌɛʃɪˈrɪkiəˈkoʊlaɪ/; commonly abbreviated E. coli) is a Gram-negative gammaproteobacterium commonly found in the lower intestine of warm-blooded organisms (endotherms). The descendants of two isolates, K-12 and B strain, are used routinely in molecular biology as both a tool and a model organism. Read more...
The African clawed frog (Xenopus laevis, also known as the xenopus, African clawed toad, African claw-toed frog or the platanna) is a species of African aquatic frog of the family Pipidae. Its name is derived from the three short claws on each hind foot, which it uses to tear apart its food. The word Xenopus means "strange foot" and laevis means "smooth".
The species is found throughout much of Sub-Saharan Africa (Nigeria and Sudan to South Africa), and in isolated, introduced populations in North America, South America, and Europe. All species of the family Pipidae are tongueless, toothless and completely aquatic. They use their hands to shove food in their mouths and down their throats and a hyobranchial pump to draw or suck things in their mouth. Pipidae have powerful legs for swimming and lunging after food. They also use the claws on their feet to tear pieces of large food. They lack true ears, but have lateral lines running down the length of the body and underside, which is how they can sense movements and vibrations in the water. They use their sensitive fingers, sense of smell, and lateral line system to find food. Pipidae are scavengers and will eat almost anything living, dying, or dead and any type of organic waste. Read more...
Chlamydomonas reinhardtii is a single-cell green alga about 10 micrometres in diameter that swims with two flagella. It has a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an "eyespot" that senses light.
Chlamydomonas species are widely distributed worldwide in soil and fresh water. Chlamydomonas reinhardtii is an especially well studied biological model organism, partly due to its ease of culturing and the ability to manipulate its genetics. When illuminated, C. reinhardtii can grow photoautotrophically, but it can also grow in the dark if supplied with organic carbon. Commercially, C. reinhardtii is of interest for producing biopharmaceuticals and biofuel, as well being a valuable research tool in making hydrogen. Read more...
Enterobacteria phage λ (lambda phage, coliphage λ) is a bacterial virus, or bacteriophage, that infects the bacterial species Escherichia coli (E. coli). It was discovered by Esther Lederberg in 1950 when she noticed that streaks of mixtures of two E. coli strains, one of which treated with ultraviolet light, was "nibbled and plaqued". The wild type of this virus has a temperate lifecycle that allows it to either reside within the genome of its host through lysogeny or enter into a lytic phase (during which it kills and lyses the cell to produce offspring); mutant strains are unable to lysogenize cells – instead, they grow and enter the lytic cycle after superinfecting an already lysogenized cell.
The phage particle consists of a head (also known as a capsid), a tail, and tail fibers (see image of virus below). The head contains the phage's double-strand linear DNA genome. During infection, the phage particle recognizes and binds to its host, E. coli, causing DNA in the head of the phage to be ejected through the tail into the cytoplasm of the bacterial cell. Usually, a "lytic cycle" ensues, where the lambda DNA is replicated and new phage particles are produced within the cell. This is followed by cell lysis, releasing the cell contents, including virions that have been assembled, into the environment. However, under certain conditions, the phage DNA may integrate itself into the host cell chromosome in the lysogenic pathway. In this state, the λ DNA is called a prophage and stays resident within the host's genome without apparent harm to the host. The host is termed a lysogen when a prophage is present. This prophage may enter the lytic cycle when the lysogen enters a stressed condition. Read more...
The zebrafish (Danio rerio) is a freshwater fish belonging to the minnow family (Cyprinidae) of the order Cypriniformes. Native to the Himalayan region, it is a popular aquarium fish, frequently sold under the trade name zebra danio (and thus often called a "tropical fish" although not native to the tropics). The zebrafish is also an important and widely used vertebrate model organism in scientific research. It is particularly notable for its regenerative abilities, and has been modified by researchers to produce many transgenic strains. Read more...
Maize (/meɪz/ MAYZ; Zea mays subsp. mays, from Spanish: maíz after Taino: mahiz), also known as corn, is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The leafy stalk of the plant produces pollen inflorescences and separate ovuliferous inflorescences called ears that yield kernels or seeds, which are fruits.
Maize has become a staple food in many parts of the world, with the total production of maize surpassing that of wheat or rice. However, little of this maize is consumed directly by humans: most is used for corn ethanol, animal feed and other, such as corn starch and corn syrup. The six major types of maize are dent corn, flint corn, pod corn, popcorn, flour corn, and sweet corn. Read more...
Neurospora crassa is a type of red bread mold of the phylum Ascomycota. The genus name, meaning "nerve spore" in Greek, refers to the characteristic striations on the spores. The first published account of this fungus was from an infestation of French bakeries in 1843.
N. crassa is used as a model organism because it is easy to grow and has a haploid life cycle that makes genetic analysis simple since recessive traits will show up in the offspring. Analysis of genetic recombination is facilitated by the ordered arrangement of the products of meiosis in Neurospora ascospores. Its entire genome of seven chromosomes has been sequenced. Read more...
The albino laboratory rat with its red eyes and white fur is an iconic model organism for scientific research in a variety of fields.
A laboratory rat or lab rat is a rat of the species Rattus norvegicus domesticus which is bred and kept for scientific research. While less commonly used for research than mice, rats have served as an important animal model for research in psychology and biomedical science. Read more...
Medicago truncatula, the barrelclover, strong-spined medick, barrel medic, or barrel medick, is a small annual legume native to the Mediterranean region that is used in genomic research. It is a low-growing, clover-like plant 10–60 centimetres (3.9–23.6 in) tall with trifoliate leaves. Each leaflet is rounded, 1–2 centimetres (0.39–0.79 in) long, often with a dark spot in the center. The flowers are yellow, produced singly or in a small inflorescence of two to five together; the fruit is a small, spiny pod.
This species is studied as a model organism for legume biology because it has a small diploid genome, is self-fertile, has a rapid generation time and prolific seed production, is amenable to genetic transformation, and its genome has been sequenced. Read more...
Tetrahymena is a genus of free-living ciliates that can also switch from commensalistic to pathogenic modes of survival. They are common in freshwater ponds. Tetrahymena species used as model organisms in biomedical research are T. thermophila and T. pyriformis. Read more...
An albino SCID laboratory mouse
The laboratory mouse is a small mammal of the order Rodentia which is bred and used for scientific research. Laboratory mice are usually of the species Mus musculus. They are the most commonly used mammalian research model and are used for research in genetics, 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.
Other mouse species sometimes used in laboratory research include the American white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus). Read more...
Drosophila melanogaster is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is known generally as the common fruit fly (though inaccurately) or vinegar fly. Starting with Charles W. Woodworth's proposal of the use of this species as a model organism, D. melanogaster continues to be widely used for biological research in genetics, physiology, microbial pathogenesis, and life history evolution. As of 2017, eight Nobel prizes had been awarded for research using Drosophila.
Drosophila is typically used in research because it can be readily reared in the laboratory, has only four pairs of chromosomes, breeds quickly, and lays many eggs. Its geographic range includes all continents, including islands. D. melanogaster is a common pest in homes, restaurants, and other places where food is served. Read more...
Caenorhabditis elegans (/ˌsiːnoʊræbˈdaɪtəsˈɛləɡænz/) is a free-living, transparent nematode, about 1 mm in length, that lives in temperate soil environments. It is the type species of its genus.
The name is a blend of the Greek caeno- (recent), rhabditis (rod-like) and Latin elegans (elegant). In 1900, Maupas initially named it Rhabditides elegans, Osche placed it in the subgenus Caenorhabditis in 1952, and in 1955, Dougherty raised Caenorhabditis to the status of genus.
C. elegans is an unsegmented pseudocoelomate and lacks respiratory or circulatory systems. The majority of these nematodes are hermaphrodites and a few are males. Males have specialised tails for mating that include spicules. Read more...
Saccharomyces cerevisiae (/ˌsɛrɪˈvɪsiiː/) is a species of yeast. It has been instrumental to winemaking, baking, and brewing since ancient times. It is believed to have been originally isolated from the skin of grapes (one can see the yeast as a component of the thin white film on the skins of some dark-colored fruits such as plums; it exists among the waxes of the cuticle). It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like Escherichia coli as the model bacterium. It is the microorganism behind the most common type of fermentation. S. cerevisiae cells are round to ovoid, 5–10 μm in diameter. It reproduces by a division process known as budding.
Many proteins important in human biology were first discovered by studying their homologs in yeast; these proteins include cell cycle proteins, signaling proteins, and protein-processing enzymes. S. cerevisiae is currently the only yeast cell known to have Berkeley bodies present, which are involved in particular secretory pathways. Antibodies against S. cerevisiae are found in 60–70% of patients with Crohn's disease and 10–15% of patients with ulcerative colitis (and 8% of healthy controls). Read more...
Arabidopsis thaliana, the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. A. thaliana is considered a weed; it is found by roadsides and in disturbed land.
A winter annual with a relatively short life cycle, A. thaliana is a popular model organism in plant biology and genetics. For a complex multicellular eukaryote, A. thaliana has a relatively small genome of approximately 135 megabase pairs (Mbp). It was the first plant to have its genome sequenced, and is a popular tool for understanding the molecular biology of many plant traits, including flower development and light sensing. Read more...
Selected model organisms in general
The brown rat (Rattus norvegicus), also known as the common rat, street rat, sewer rat, Hanover rat, Norway rat, Norwegian rat, Parisian rat, water rat or wharf rat, is one of the best known and most common rats.
One of the largest muroids, it is a brown or grey rodent with a head and body length of up to 28 cm (11 in) long, and a slightly shorter tail. It weighs between 140 and 500 g (4.9 and 17.6 oz). Thought to have originated in northern China, this rodent has now spread to all continents except Antarctica, and is the dominant rat in Europe and much of North America, making it by at least this particular definition the most successful mammal on the planet alongside humans. With rare exceptions, the brown rat lives wherever humans live, particularly in urban areas. Read more...- Oscarella carmela, commonly known as the slime sponge, is a species of sponge in the order Homosclerophorida that was first described in 2004 by G. Muricy and J.S. Pearse. It is believed to be native to intertidal waters in the north east temperate Pacific Ocean and was first found in seawater aquaria in that region. It is used as a model organism in evolutionary biology. Read more...
The western clawed frog (Xenopus tropicalis) is a species of frog in the family Pipidae, also known as tropical clawed frog. It is the only species in the genus Xenopus to have a diploid genome. Its genome has been sequenced, making it a significant model organism for genetics that complements the related species Xenopus laevis (the African clawed frog), a widely used vertebrate model for developmental biology. X. tropicalis also has a number of advantages over X. laevis in research, such as a much shorter generation time (<5 months), smaller size (4–6 cm (1.6–2.4 in) body length), and a larger number of eggs per spawn.
It is found in Benin, Burkina Faso, Cameroon, Ivory Coast, Equatorial Guinea, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Nigeria, Senegal, Sierra Leone, Togo, and possibly Mali. Its natural habitats are subtropical or tropical moist lowland forests, moist savanna, rivers, intermittent rivers, swamps, freshwater lakes, intermittent freshwater lakes, freshwater marshes, intermittent freshwater marshes, rural gardens, heavily degraded former forests, water storage areas, ponds, aquaculture ponds, and canals and ditches. Read more...
European fire-bellied toad (Bombina bombina)
The fire-bellied toads or fire belly toads are a group of eight species of small toads (most species typically no longer than 1.6 in or 4.1 cm) belonging to the genus Bombina.
The name "fire-bellied" is derived from the brightly colored red- or yellow-and-black patterns on the toads' ventral regions, which act as aposematic coloration, a warning to predators of the toads' reputedly foul taste. The other parts of the toads' skins are green or dark brown. When confronted with a potential predator, these toads commonly engage in an Unkenreflex, "Unken-" being the combining form of "Unke", German for fire-bellied toad. In the Unkenreflex, the toad arches its back, raising its front and back legs to display the aposematic coloration of its ventral side. Read more...
Erythranthe guttata, with the common names seep monkeyflower and common yellow monkeyflower, is a yellow bee-pollinated annual or perennial plant. It was formerly known as Mimulus guttatus.
Erythranthe guttata is a model organism for studies of evolution and ecology, and in that context is still commonly known as Mimulus. There may be as many as 1000 scientific papers focused on this species. The genome is (as of 2012) being studied in depth. Read more...
SV40 is an abbreviation for simian vacuolating virus 40 or simian virus 40, a polyomavirus that is found in both monkeys and humans. It was named for the effect it produced on infected green monkey cells, which developed an unusual number of vacuoles. Like other polyomaviruses, SV40 is a DNA virus that has the potential to cause tumors in animals, but most often persists as a latent infection. SV40 has been widely studied as a model eukaryotic virus, leading to many early discoveries in eukaryotic DNA replication and transcription.
The discovery of SV40 revealed that between 1955 and 1963 around 90% of children and 60% of adults in the U.S. were inoculated with SV40-contaminated polio vaccines. Read more...
A rooster or cock (left) and hen (right)
The chicken (Gallus gallus domesticus) is a type of domesticated fowl, a subspecies of the red junglefowl. It is one of the most common and widespread domestic animals, with a total population of more than 19 billion as of 2011. There are more chickens in the world than any other bird or domesticated fowl. Humans keep chickens primarily as a source of food (consuming both their meat and eggs) and, less commonly, as pets. Originally raised for cockfighting or for special ceremonies, chickens were not kept for food until the Hellenistic period (4th–2nd centuries BC).
Genetic studies have pointed to multiple maternal origins in Southeast Asia, East Asia, and South Asia, but with the clade found in the Americas, Europe, the Middle East and Africa originating in the Indian subcontinent. From ancient India, the domesticated chicken spread to Lydia in western Asia Minor, and to Greece by the 5th century BC. Fowl had been known in Egypt since the mid-15th century BC, with the "bird that gives birth every day" having come to Egypt from the land between Syria and Shinar, Babylonia, according to the annals of Thutmose III. Read more...
The zebrafish (Danio rerio) is a freshwater fish belonging to the minnow family (Cyprinidae) of the order Cypriniformes. Native to the Himalayan region, it is a popular aquarium fish, frequently sold under the trade name zebra danio (and thus often called a "tropical fish" although not native to the tropics). The zebrafish is also an important and widely used vertebrate model organism in scientific research. It is particularly notable for its regenerative abilities, and has been modified by researchers to produce many transgenic strains. Read more...
Scathophaga stercoraria, commonly known as the yellow dung fly or the golden dung fly, is one of the most familiar and abundant flies in many parts of the Northern Hemisphere. As its common name suggests, it is often found on the feces of large mammals, such as horses, cattle, sheep, deer, and wild boar, where it goes to breed. The distribution of S. stercoraria is likely influenced by human agriculture, especially in Northern Europe and North America. The Scathophaga are integral in the animal kingdom due to their role in the natural decomposition of dung in fields. They are also very important in the scientific world due to their short lifecycles and susceptibility to experimental manipulations, thus have contributed significant knowledge about animal behavior. Read more...
Medicago truncatula, the barrelclover, strong-spined medick, barrel medic, or barrel medick, is a small annual legume native to the Mediterranean region that is used in genomic research. It is a low-growing, clover-like plant 10–60 centimetres (3.9–23.6 in) tall with trifoliate leaves. Each leaflet is rounded, 1–2 centimetres (0.39–0.79 in) long, often with a dark spot in the center. The flowers are yellow, produced singly or in a small inflorescence of two to five together; the fruit is a small, spiny pod.
This species is studied as a model organism for legume biology because it has a small diploid genome, is self-fertile, has a rapid generation time and prolific seed production, is amenable to genetic transformation, and its genome has been sequenced. Read more...
Bacillus subtilis, known also as the hay bacillus or grass bacillus, is a Gram-positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of ruminants and humans. A member of the genus Bacillus, B. subtilis is rod-shaped, and can form a tough, protective endospore, allowing it to tolerate extreme environmental conditions. B. subtilis has historically been classified as an obligate aerobe, though evidence exists that it is a facultative anaerobe. B. subtilis is considered the best studied Gram-positive bacterium and a model organism to study bacterial chromosome replication and cell differentiation. It is one of the bacterial champions in secreted enzyme production and used on an industrial scale by biotechnology companies. Read more...
Mycoplasma genitalium (MG, commonly known as Mgen), is a sexually transmitted, small and pathogenic bacterium that lives on the ciliated epithelial cells of the urinary and genital tracts in humans. Mgen is a recognised sexually transmitted infection, with increasing prevalence worldwide resistance to multiple antibiotics, including azithromycin which until recently was the most reliable line of antimicrobial defence. The causative agent was first isolated from meatal swabs (urogenital tract) of humans in 1981, and was eventually identified as a new species of Mycoplasma in 1983. It can cause significant morbidity in men and women. It is also a recognised risk factor for HIV transmission with higher occurrences in homosexual men and those previously treated with the azithromycin antibiotics.
Specifically, it causes urethritis in both men and women, and also cervicitis and pelvic inflammation in women. It presents clinically similar symptoms to that of Chlamydia trachomatis infection and has shown higher incidence rates, compared to both Chlamydia trachomatis and Neisseria gonorrhoeae infections in some populations. Its complete genome sequence was published in 1995 (size 0.58 Mbp, with 475 genes). It was regarded as a cellular unit with the smallest genome size (in Mbp) until 2003 when a new species of Archaea, namely Nanoarchaeum equitans, was sequenced (0.49 Mbp, with 540 genes). However, Mgen still has the smallest genome of any known (naturally occurring) self-replicating organism and thus is often the organism of choice in minimal-genome research. Read more...
Parhyale hawaiensis is an amphipod crustacean species that is used in developmental and genetic analyses. Read more...
Ciona intestinalis (sometimes known by the common name of vase tunicate) is an ascidian (sea squirt), a tunicate with very soft tunic. Its Latin name means, literally, "pillar of intestines", referring to the fact that its body is a soft, translucent column-like structure, resembling a mass of intestines sprouting from a rock. It is a globally distributed cosmopolitan species. Since Linnaeus described the species, Ciona intestinalis has been used as a model invertebrate chordate in developmental biology and genomics. Recent studies have shown that there are at least two, possibly four, sister species. By anthropogenic means, the species has invaded various parts of the world and is known as an invasive species.
Although Linnaeus first categorised this species as a kind of mollusk, Alexander Kovalevsky found a tadpole-like larval stage during development that shows similarity to vertebrates. Recent molecular phylogenetic studies as well as phylogenomic studies support that sea squirts are the closest invertebrate relatives of vertebrates. Its full genome has been sequenced using a specimen from Half Moon Bay in California, USA, showing a very small genome size, less than 1/20 of the human genome, but having a gene corresponding to almost every family of genes in vertebrates. Read more...
The Atlantic purple sea urchin (Arbacia punctulata) is a species of sea urchins from the family Arbaciidae, native to the Atlantic Ocean. Read more...
Euprymna scolopes, also known as the Hawaiian bobtail squid, is a species of bobtail squid in the family Sepiolidae native to the central Pacific Ocean, where it occurs in shallow coastal waters off the Hawaiian Islands and Midway Island. The type specimen was collected off the Hawaiian Islands and is deposited at the National Museum of Natural History in Washington, D.C..
Euprymna scolopes grows to 30 mm (1.2 in) in mantle length. Hatchlings weigh 0.005 g (0.00018 oz) and mature in 80 days. Adults weigh up to 2.67 g (0.094 oz). Read more...- Tobacco BY-2 cells is a cell line of plant cells, which was established from a callus induced on a seedling of Nicotiana tabacum cv. BY-2 (cultivar Bright Yellow - 2 of the tobacco plant). Read more...
The Coelopidae or kelp flies are a family of Acalyptratae flies (order Diptera), they are sometimes also called seaweed flies, though both terms are used for a number of seashore Diptera. Fewer than 40 species occur worldwide. The family is found in temperate areas, with species occurring in the southern Afrotropical, Holarctic, and Australasian (which has the most species) regions. Read more...
Hydra /ˈhaɪdrə/ is a genus of small, fresh-water organisms of the phylum Cnidaria and class Hydrozoa. They are native to the temperate and tropical regions. Biologists are especially interested in Hydra because of their regenerative ability — they do not appear to die of old age, or indeed to age at all. Read more...
Daphnia, a genus of small planktonic crustaceans, are 0.2–5 millimetres (0.01–0.20 in) in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because their saltatory (Wiktionary) swimming style resembles the movements of fleas. Daphnia live in various aquatic environments ranging from acidic swamps to freshwater lakes and ponds.
The two most readily available species of Daphnia are D. pulex (small and most common) and D. magna (large). They are often associated with a related genus in the order Cladocera: Moina, which is in the Moinidae family instead of Daphniidae and is much smaller than D. pulex (approximately half the maximum length). Daphnia eggs for sale are generally enclosed in ephippia (a thick shell, consisting of two chitinous plates, that encloses and protects the winter eggs of a cladoceran). Read more...
Caulobacter crescentus is a Gram-negative, oligotrophic bacterium widely distributed in fresh water lakes and streams.
Caulobacter is an important model organism for studying the regulation of the cell cycle, asymmetric cell division, and cellular differentiation. Caulobacter daughter cells have two very different forms. One daughter is a mobile "swarmer" cell that has a single flagellum at one cell pole that provides swimming motility for chemotaxis. The other daughter, called the "stalked" cell has a tubular stalk structure protruding from one pole that has an adhesive holdfast material on its end, with which the stalked cell can adhere to surfaces. Swarmer cells differentiate into stalked cells after a short period of motility. Chromosome replication and cell division only occurs in the stalked cell stage. Its name derives from its crescent shape caused by the protein crescentin, discovered by Christine Jacobs-Wagner's laboratory. Its use as a model originated with developmental biologist Lucy Shapiro. Read more...
Tubifex tubifex, also called the sludge worm, or sewage worm, is a species of tubificid segmented worm that inhabits the sediments of lakes and rivers on several continents. Tubifex probably includes several species, but distinguishing between them is difficult because the reproductive organs, commonly used in species identification, are resorbed after mating, and because the external characteristics of the worm vary with changes in salinity. These worms ingest sediments, selectively digest bacteria, and absorb molecules through their body walls.
The worms can survive with little oxygen by waving hemoglobin-rich tail ends to exploit all available oxygen, and can exchange carbon dioxide and oxygen through their thin skins, in a manner similar to frogs. They can also survive in areas heavily polluted with organic matter that almost no other species can endure. By forming a protective cyst and lowering its metabolic rate, T. tubifex can survive drought and food shortage. Encystment may also function in the dispersal of the worm.
They usually inhabit the bottom sediments of lakes, rivers, and occasionally sewer lines and outlets. Read more...
Arabidopsis thaliana, the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. A. thaliana is considered a weed; it is found by roadsides and in disturbed land.
A winter annual with a relatively short life cycle, A. thaliana is a popular model organism in plant biology and genetics. For a complex multicellular eukaryote, A. thaliana has a relatively small genome of approximately 135 megabase pairs (Mbp). It was the first plant to have its genome sequenced, and is a popular tool for understanding the molecular biology of many plant traits, including flower development and light sensing. Read more...
Enterobacteria phage λ (lambda phage, coliphage λ) is a bacterial virus, or bacteriophage, that infects the bacterial species Escherichia coli (E. coli). It was discovered by Esther Lederberg in 1950 when she noticed that streaks of mixtures of two E. coli strains, one of which treated with ultraviolet light, was "nibbled and plaqued". The wild type of this virus has a temperate lifecycle that allows it to either reside within the genome of its host through lysogeny or enter into a lytic phase (during which it kills and lyses the cell to produce offspring); mutant strains are unable to lysogenize cells – instead, they grow and enter the lytic cycle after superinfecting an already lysogenized cell.
The phage particle consists of a head (also known as a capsid), a tail, and tail fibers (see image of virus below). The head contains the phage's double-strand linear DNA genome. During infection, the phage particle recognizes and binds to its host, E. coli, causing DNA in the head of the phage to be ejected through the tail into the cytoplasm of the bacterial cell. Usually, a "lytic cycle" ensues, where the lambda DNA is replicated and new phage particles are produced within the cell. This is followed by cell lysis, releasing the cell contents, including virions that have been assembled, into the environment. However, under certain conditions, the phage DNA may integrate itself into the host cell chromosome in the lysogenic pathway. In this state, the λ DNA is called a prophage and stays resident within the host's genome without apparent harm to the host. The host is termed a lysogen when a prophage is present. This prophage may enter the lytic cycle when the lysogen enters a stressed condition. Read more...
Locusts are grasshoppers, such as this migratory locust (Locusta migratoria), that have entered into a migratory phase of their life.
Locusts are certain species of short-horned grasshoppers in the family Acrididae that have a swarming phase. These insects are usually solitary, but under certain circumstances they become more abundant and change their behaviour and habits, becoming gregarious. No taxonomic distinction is made between locust and grasshopper species; the basis for the definition is whether a species forms swarms under intermittently suitable conditions.
In the solitary phase, these grasshoppers are innocuous, their numbers are low, and they do not pose a major economic threat to agriculture. However, under suitable conditions of drought followed by rapid vegetation growth, serotonin in their brains triggers a dramatic set of changes: they start to breed abundantly, becoming gregarious and nomadic (loosely described as migratory) when their populations become dense enough. They form bands of wingless nymphs which later become swarms of winged adults. Both the bands and the swarms move around and rapidly strip fields and cause damage to crops. The adults are powerful fliers; they can travel great distances, consuming most of the green vegetation wherever the swarm settles. Read more...
Chlamydomonas reinhardtii is a single-cell green alga about 10 micrometres in diameter that swims with two flagella. It has a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an "eyespot" that senses light.
Chlamydomonas species are widely distributed worldwide in soil and fresh water. Chlamydomonas reinhardtii is an especially well studied biological model organism, partly due to its ease of culturing and the ability to manipulate its genetics. When illuminated, C. reinhardtii can grow photoautotrophically, but it can also grow in the dark if supplied with organic carbon. Commercially, C. reinhardtii is of interest for producing biopharmaceuticals and biofuel, as well being a valuable research tool in making hydrogen. Read more...
Marchantia polymorpha, sometimes known as the common liverwort or umbrella liverwort, is a large liverwort with a wide distribution around the world. It is variable in appearance and has several subspecies. It is dioicous, having separate male and female plants. Read more...
The house mouse (Mus musculus) is a small mammal of the order Rodentia, characteristically having a pointed snout, small rounded ears, and a long naked or almost hairless tail. It is one of the most abundant species of the genus Mus. Although a wild animal, the house mouse mainly lives in association with humans.
The house mouse has been domesticated as the pet or fancy mouse, and as the laboratory mouse, which is one of the most important model organisms in biology and medicine. The complete mouse reference genome was sequenced in 2002. Read more...
Galleria mellonella, the greater wax moth or honeycomb moth, is a moth of the family Pyralidae. G. mellonella is found throughout the world. It is one of two species of wax moths, with the other being the lesser wax moth. G. mellonella eggs are laid in the spring, and they have four life stages. Males are able to generate ultrasonic sound pulses, which, along with pheromones, are used in mating. The larvae of G. mellonella are also often used as a model organism in research.
The greater wax moth is well known for its parasitization of honeybees and their hives. Because of the economic loss caused by this species, several control methods including heat treatment and chemical fumigants such as carbon dioxide have been used. Read more...
The Carolina anole (Anolis carolinensis) (US: /əˈnoʊ.li/ (
listen)) is an arboreal anole lizard native to the southeastern United States (west to Texas) and introduced elsewhere. Other common names include the American green anole, American anole, and red-throated anole. It is also sometimes referred to as the American chameleon due to its ability to change color from several brown hues to bright green, and its somewhat similar appearance and diet preferences. However it is not a true chameleon and the nickname is misleading. Read more...
The zebra finch (Taeniopygia guttata) is the most common estrildid finch of Central Australia and ranges over most of the continent, avoiding only the cool moist south and some areas of the tropical far north. It can also be found natively in Indonesia and East Timor. The bird has been introduced to Puerto Rico and Portugal. Read more...
Symsagittifera roscoffensis, whose vernacular name is the "Roscoff worm" or "mint-sauce worm", is a marine flatworm belonging to the phylum of Xenacoelomorpha. The origin and nature of the green color of this worm stimulated the curiosity of zoologists early on. It is due to the partnership between the animal and a green micro-algae, the species Tetraselmis convolutae, hosted under its epidermis. It is the photosynthetic activity of the micro-algae in hospite that provides the essential nutrients for the worm. This partnership is called photosymbiosis, from "photo", "light", and symbiosis "who lives with". These photosynthetic marine animals live in colonies (up to several million individuals) on the tidal zone. Read more...
Nothobranchius furzeri, the turquoise killifish, is a species of aplocheilid fish native to Africa where it is only known from Zimbabwe and Mozambique. This annual killifish inhabits ephemeral pools in semi-arid areas with scarce and erratic precipitations and have adapted to the routine drying of their environment by evolving desiccation-resistant eggs that can remain dormant in the dry mud for one and maybe more years by entering into diapause. Due to very short duration of the rain season, the natural lifespan of these animals is limited to a few months and their captive lifespan is likewise short, making them an attractive model system for ageing and disease research. Tandem repeats comprise 21% of the species' genome, an abnormally high proportion, which has been suggested as a factor in its fast ageing. The species has the fastest known sexual maturity among vertebrates, going from hatchling to an adult ready to breed in only 14 days.
This species can reach a total length of 6.5 cm (2.6 in). Read more...
Takifugu rubripes, commonly known as the Japanese puffer, Tiger puffer, or torafugu (Japanese: 虎河豚), is a pufferfish in the genus Takifugu. It is distinguished by a very small genome that has been fully sequenced because of its use as a model species and is in widespread use as a reference in genomics. Read more...
The cat (Felis catus, or Felis silvestris catus, literally "woodland cat"), often referred to as the domestic cat to distinguish from other felids and felines, is a small, typically furry, carnivorous mammal. It is often called house cat when kept as indoor pet or feral/feral domestic cat when wild. It is often valued by humans for companionship and for its ability to hunt vermin. There are more than seventy cat breeds recognized by various cat registries.
Cats are similar in anatomy to the other felids, with a strong flexible body, quick reflexes, sharp teeth and retractable claws adapted to killing small prey. Cat senses fit a crepuscular and predatory ecological niche. Cats can hear sounds too faint or too high in frequency for human ears, such as those made by mice and other small animals. They can see in near darkness. Like most other mammals, cats have poorer color vision and a better sense of smell than humans. Cats, despite being solitary hunters, are a social species, and cat communication includes the use of a variety of vocalizations (mewing, purring, trilling, hissing, growling and grunting) as well as cat pheromones and types of cat-specific body language. Read more...
Trichoplax adhaerens is the only extant representative of the phylum Placozoa, which is a basal group of multicellular animals (metazoa). Trichoplax are very flat organisms around a millimetre in diameter, lacking any organs or internal structures. They have two cellular layers: the top epitheloid layer is made of ciliated "cover cells" flattened toward the outside of the organism, and the bottom layer is made up of cylinder cells that possess cilia used in locomotion, and gland cells that lack cilia. Between these layers is the fibre syncytium, a liquid-filled cavity strutted open by star-like fibres.
Trichoplax feed by absorbing food particles—mainly microbes—with their underside. They generally reproduce asexually, by dividing or budding, but can also reproduce sexually. Though Trichoplax has a small genome in comparison to other animals, nearly 87% of its 11,514 predicted protein-coding genes are identifiably similar to known genes in other animals. Read more...
Stentor coeruleus is a protist of the Stentor genus. It belongs to the Stentoridae family which is characterized by being a very large ciliate that measures 0.5 to 2 millimetres when fully extended.
Stentor coeruleus specifically appears as a very large trumpet. It contains a macronucleus that looks like a string of beads that are contained within a ciliate that is blue to blue-green in color. Being that it has many myonemes, it has the ability to contract into a ball. It has the ability to swim while both fully extended or contracted. Read more...
Schizosaccharomyces pombe, also called "fission yeast", is a species of yeast used in traditional brewing and as a model organism in molecular and cell biology. It is a unicellular eukaryote, whose cells are rod-shaped. Cells typically measure 3 to 4 micrometres in diameter and 7 to 14 micrometres in length. Its genome, which is approximately 14.1 million base pairs, is estimated to contain 4,970 protein-coding genes and at least 450 non-coding RNAs.
These cells maintain their shape by growing exclusively through the cell tips and divide by medial fission to produce two daughter cells of equal size, which makes them a powerful tool in cell cycle research. Read more...
Enterobacteria phage T4 is a bacteriophage that infects Escherichia coli bacteria. The T4 phage is a member of the T-even phages, a group including enterobacteriophages T2 and T6. T4 is capable of undergoing only a lytic lifecycle and not the lysogenic lifecycle. Read more...
The axolotl (/ˈæksəlɒtəl/, from Classical Nahuatl: āxōlōtl [aːˈʃoːloːtɬ] (
listen); plural axolotls or rarely axolomeh), Ambystoma mexicanum, also known as the Mexican walking fish, is a neotenic salamander related to the tiger salamander. Although the axolotl is colloquially known as a "walking fish", it is not a fish, but an amphibian. The species was originally found in several lakes, such as Lake Xochimilco underlying Mexico City. Axolotls are unusual among amphibians in that they reach adulthood without undergoing metamorphosis. Instead of developing lungs and taking to the land, adults remain aquatic and gilled.
Axolotls should not be confused with waterdogs, the larval stage of the closely related tiger salamanders (A. tigrinum and A. mavortium), which are widespread in much of North America and occasionally become neotenic. Neither should they be confused with mudpuppies (Necturus spp.), fully aquatic salamanders that are not closely related to the axolotl but bear a superficial resemblance. Read more...
Coprinopsis cinerea is a species of mushroom in the family Psathyrellaceae. Commonly known as the gray shag, it is edible, but must be used promptly after collecting.
Coprinopsis cinerea is an important model organism for studying fungal sex and mating types, mushroom development, and the evolution of multicellularity of fungi. The genome sequence was published in 2010. It is considered to be particularly suited organism to study meiosis, due to its synchronous meiotic development and prolonged prophase. Read more...
Lotus, a latinization of Greek lōtos (λωτός), is a genus that includes most bird's-foot trefoils (also known as bacon-and-eggs) and deervetches and contains many dozens of species distributed worldwide. Depending on the taxonomic authority, roughly between 70 and 150 are accepted. Lotus is a genus of legumes and its members are adapted to a wide range of habitats, from coastal environments to high altitudes.
The genus Lotus is currently undergoing extensive taxonomic revision. Species native to the Americas have been moved into other genera, such as Acmispon and Hosackia, as in the second edition of The Jepson Manual. Read more...- Synechocystis is a genus of unicellular, freshwater cyanobacteria primarily represented by the strain Synechocystis sp. PCC6803. Synechocystis sp. PCC6803 is capable of both phototrophic growth by oxygenic photosynthesis during light periods and heterotrophic growth by glycolysis and oxidative phosphorylation during dark periods. Gene expression is regulated by a circadian clock and the organism can effectively anticipate transitions between the light and dark phases. Read more...
Corn smut is a plant disease caused by the pathogenic fungus Ustilago maydis that causes smut on maize and teosinte. The fungus forms galls on all above-ground parts of corn species, and is known in Mexico as the delicacy huitlacoche; which is eaten, usually as a filling, in quesadillas and other tortilla-based foods, and soups. Read more...
Leaf of Populus tremula
Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar /ˈpɒp.lər/, aspen, and cottonwood.
In the September 2006 issue of Science Magazine, the Joint Genome Institute announced that the western balsam poplar (P. trichocarpa) was the first tree whose full DNA code had been determined by DNA sequencing. Read more...
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Drosophila melanogaster, one of the most famous subjects for genetics experiments
Saccharomyces cerevisiae, one of the most intensively studied eukaryotic model organisms in molecular and cell biology
Laboratory mice, widely used in medical research
Escherichia coli is a gram-negative prokaryotic model organism
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