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97-430: T-boxes are especially important to the development of embryos, found in zebrafish oocyte by Bruce et al 2003 and Xenopus laevis oocyte by Xanthos et al 2001. They are also expressed in later stages, including adult mouse and rabbit studied by Szabo et al 2000. Mutations in the first one found caused short tails in mice, and thus the protein encoded was named brachyury , Greek for "short-tail". In mice this gene

194-432: A homozygous embryo. The zebrafish embryos are transparent and they develop outside of the uterus, which allows scientists to study the details of development starting from fertilization and continuing throughout development. The zebrafish is also demonstrably similar to mammalian models and humans in toxicity testing, and exhibits a diurnal sleep cycle with similarities to mammalian sleep behavior. However, zebrafish are not

291-605: A solute carrier that appeared to be required for melanin production, and confirmed its function with a Morpholino knockdown. The orthologous gene was then characterized in humans and a one base pair difference was found to strongly segregate fair-skinned Europeans and dark-skinned Africans. Zebrafish with the nacre mutation have since been bred with fish with a roy orbison (roy) mutation to make Casper strain fish that have no melanophores or iridophores, and are transparent into adulthood. These fish are characterized by uniformly pigmented eyes and translucent skin. Transgenesis

388-479: A chromosomal segment of interest, aiding in targeted transgenesis. The Cre transposase is important in the catalytic cleavage of the base pairs present at the carefully positioned loxP sites, permitting more specific insertions of the transgenic donor plasmid of interest. To overcome the limitations and low yields that transposon-mediated and Cre-loxP transformation methods produce, the bacteriophage ΦC31 has recently been utilized. Recent breakthrough studies involve

485-497: A dedicated online database of genetic, genomic, and developmental information, the Zebrafish Information Network (ZFIN). The Zebrafish International Resource Center (ZIRC) is a genetic resource repository with 29,250 alleles available for distribution to the research community. D. rerio is also one of the few fish species to have been sent into space . Research with D. rerio has yielded advances in

582-404: A defect in cells, and transgenesis seeks to produce a genetically modified organism by incorporating the specific transgene into every cell and changing the genome . Transgenesis will therefore change the germ cells, not only the somatic cells, in order to ensure that the transgenes are passed down to the offspring when the organisms reproduce. Transgenes alter the genome by blocking the function of

679-515: A host gene; they can either replace the host gene with one that codes for a different protein, or introduce an additional gene. The first transgenic organism was created in 1974 when Annie Chang and Stanley Cohen expressed Staphylococcus aureus genes in Escherichia coli . In 1978, yeast cells were the first eukaryotic organisms to undergo gene transfer. Mouse cells were first transformed in 1979, followed by mouse embryos in 1980. Most of

776-555: A key element in a process known as recombinase-mediated cassette exchange (RMCE). While it has shown to have a lower efficiency of transgenic transformation than the P element transposases, Cre greatly lessens the labor-intensive abundance of balancing random P insertions. Cre aids in the targeted transgenesis of the DNA gene segment of interest, as it supports the mapping of the transgene insertion sites, known as loxP sites. These sites, unlike P elements, can be specifically inserted to flank

873-597: A laboratory animal was pioneered by the American molecular biologist George Streisinger and his colleagues at the University of Oregon in the 1970s and 1980s; Streisinger's zebrafish clones were among the earliest successful vertebrate clones created. Its importance has been consolidated by successful large-scale forward genetic screens (commonly referred to as the Tübingen/Boston screens). The fish has

970-467: A large variety of plastic items, disrupt the endocannabinoid system and thereby affect reproduction in a sex-specific manner. Zebrafish feeding practices vary significantly across different developmental stages, reflecting their changing nutritional needs. For newly hatched larvae, which begin feeding at approximately 5 days post-fertilization (dpf), small live prey such as Paramecium or rotifers are commonly used until they reach 9–15 dpf. This early diet

1067-550: A native Japanese species, Brassica rapa – was found in Japan in 2011 after having been identified in 2006 in Québec , Canada. They were persistent over a six-year study period, without herbicide selection pressure and despite hybridization with the wild form. This was the first report of the introgression —the stable incorporation of genes from one gene pool into another—of an herbicide-resistance transgene from Brassica napus into

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1164-460: A new strain of zebrafish, named Casper, whose adult bodies had transparent skin. This allows for detailed visualization of cellular activity, circulation, metastasis and many other phenomena. In 2019 researchers published a crossing of a prkdc and a IL2rga strain that produced transparent, immunodeficient offspring, lacking natural killer cells as well as B - and T-cells . This strain can be adapted to 37 °C (99 °F) warm water and

1261-592: A number of commercially available global platforms exist for analysis of both gene expression by microarrays and promoter regulation using ChIP-on-chip . The Wellcome Trust Sanger Institute started the zebrafish genome sequencing project in 2001, and the full genome sequence of the Tuebingen reference strain is publicly available at the National Center for Biotechnology Information (NCBI)'s Zebrafish Genome Page . The zebrafish reference genome sequence

1358-529: A role in limb development , and play a major role in limb bud initiation specifically. For instance, in chickens TBX4 specifies hindlimb status while Tbx5 specifies forelimb status. The activation of these proteins by Hox genes initiates signaling cascades that involve the Wnt signaling pathway and FGF signals in limb buds. Ultimately, TBX4 and TBX5 lead to the development of apical ectodermal ridge (AER) and zone of polarizing activity (ZPA) signaling centers in

1455-412: A specialised protein , known as fibroblast growth factor , to ensure their spinal cords heal without glial scarring after injury. In addition, hair cells of the posterior lateral line have also been found to regenerate following damage or developmental disruption. Study of gene expression during regeneration has allowed for the identification of several important signaling pathways involved in

1552-764: A transgene requires the assembly of a few main parts. The transgene must contain a promoter , which is a regulatory sequence that will determine where and when the transgene is active, an exon , a protein coding sequence (usually derived from the cDNA for the protein of interest), and a stop sequence. These are typically combined in a bacterial plasmid and the coding sequences are typically chosen from transgenes with previously known functions. Transgenic or genetically modified organisms , be they bacteria, viruses or fungi, serve many research purposes. Transgenic plants , insects, fish and mammals (including humans) have been bred. Transgenic plants such as corn and soybean have replaced wild strains in agriculture in some countries (e.g.

1649-553: A transgene with the desired sequence is inserted into an isolated mouse blastocyst using electroporation . Then, homologous recombination occurs naturally within some cells, replacing the gene of interest with the designed transgene. Through this process, researchers were able to demonstrate that a transgene can be integrated into the genome of an animal, serve a specific function within the cell, and be passed down to future generations. Oncomice are another genetically modified mouse species created by inserting transgenes that increase

1746-414: A transgene, in a process known as transgenesis , has the potential to change the phenotype of an organism. Transgene describes a segment of DNA containing a gene sequence that has been isolated from one organism and is introduced into a different organism. This non-native segment of DNA may either retain the ability to produce RNA or protein in the transgenic organism or alter the normal function of

1843-467: A transgenic plant species is golden rice . In 1997, five million children developed xerophthalmia , a medical condition caused by vitamin A deficiency, in Southeast Asia alone. Of those children, a quarter million went blind. To combat this, scientists used biolistics to insert the daffodil phytoene synthase gene into Asia indigenous rice cultivars . The daffodil insertion increased

1940-512: A universally ideal research model; there are a number of disadvantages to their scientific use, such as the absence of a standard diet and the presence of small but important differences between zebrafish and mammals in the roles of some genes related to human disorders. Zebrafish have the ability to regenerate their heart and lateral line hair cells during their larval stages. The cardiac regenerative process likely involves signaling pathways such as Notch and Wnt ; hemodynamic changes in

2037-405: A variety of different DNA repair pathways are expressed during development. Zebrafish have, in recent years, proven to be a useful model for assessing environmental pollutants that might cause DNA damage. Transgenic A transgene is a gene that has been transferred naturally, or by any of a number of genetic engineering techniques, from one organism to another. The introduction of

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2134-440: A yolk with a single enormous cell on top (see image, 0 h panel), which divides into two (0.75 h panel) and continues dividing until there are thousands of small cells (3.25 h panel). The cells then migrate down the sides of the yolk (8 h panel) and begin forming a head and tail (16 h panel). The tail then grows and separates from the body (24 h panel). The yolk shrinks over time because the fish uses it for food as it matures during

2231-422: Is 16,596 base pairs. This is within 100 base pairs of other related species of fish, and it is notably only 18 pairs longer than the goldfish ( Carassius auratus ) and 21 longer than the carp ( Cyprinus carpio ). Its gene order and content are identical to the common vertebrate form of mitochondrial DNA. It contains 13 protein -coding genes and a noncoding control region containing the origin of replication for

2328-431: Is a stub . You can help Misplaced Pages by expanding it . Zebrafish The zebrafish ( Danio rerio ) is a freshwater fish belonging to the minnow family ( Cyprinidae ) of the order Cypriniformes . Native to South Asia, it is a popular aquarium fish , frequently sold under the trade name zebra danio (and thus often called a " tropical fish " although it is both tropical and subtropical ). The zebrafish

2425-444: Is a capacity of explicit memory systems, typically associated with conscious experience . The Mauthner cells integrate a wide array of sensory stimuli to produce the escape reflex . Those stimuli are found to include the lateral line signals by McHenry et al. 2009 and visual signals consistent with looming objects by Temizer et al. 2015, Dunn et al. 2016, and Yao et al. 2016. The approximate generation time for Danio rerio

2522-493: Is a popular approach to study the function of genes in zebrafish. Construction of transgenic zebrafish is rather easy by a method using the Tol2 transposon system. Tol2 element which encodes a gene for a fully functional transposase capable of catalyzing transposition in the zebrafish germ lineage. Tol2 is the only natural DNA transposable element in vertebrates from which an autonomous member has been identified. Examples include

2619-508: Is a spotted colour morph of the zebrafish which arose due to a pigment mutation. Xanthistic forms of both the zebra and leopard pattern, along with long-finned strains, have been obtained via selective breeding programs for the aquarium trade. Various transgenic and mutant strains of zebrafish were stored at the China Zebrafish Resource Center (CZRC), a non-profit organization, which was jointly supported by

2716-405: Is able to integrate into most cells of the embryo. A known problem with gene knockdowns is that, because the genome underwent a duplication after the divergence of ray-finned fishes and lobe-finned fishes , it is not always easy to silence the activity of one of the two gene paralogs reliably due to complementation by the other paralog. Despite the complications of the zebrafish genome ,

2813-415: Is an important and widely used vertebrate model organism in scientific research, particularly developmental biology , but also gene function, oncology , teratology , and drug development , in particular pre-clinical development . It is also notable for its regenerative abilities, and has been modified by researchers to produce many transgenic strains. The zebrafish is a derived member of

2910-658: Is annotated as part of the Ensembl project , and is maintained by the Genome Reference Consortium . In 2009, researchers at the Institute of Genomics and Integrative Biology in Delhi, India, announced the sequencing of the genome of a wild zebrafish strain, containing an estimated 1.7 billion genetic letters. The genome of the wild zebrafish was sequenced at 39-fold coverage. Comparative analysis with

3007-502: Is capable of laying 200–300 eggs in one morning in approximately 5 to 10 at time. Male zebrafish are furthermore known to respond to more pronounced markings on females, i.e., "good stripes", but in a group, males will mate with whichever females they can find. What attracts females is not currently understood. The presence of plants, even plastic plants, also apparently encourages spawning. Exposure to environmentally relevant concentrations of diisononyl phthalate (DINP), commonly used in

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3104-510: Is crucial for their growth and survival, as these small organisms provide essential nutrients. As the larvae develop, from 15 dpf onwards, they are typically transitioned to a diet that includes brine shrimp nauplii and dry feeds, which are more nutritionally balanced and easier to manage in laboratory settings. For larvae aged 25 dpf, feeding rates can range from 50% to 300% of their body weight (BW) per day, depending on their size and growth requirements. As zebrafish grow into juveniles (30–90 dpf),

3201-524: Is entirely based on pre-1930 records and likely refers to close relatives only described later, notably Danio kyathit . Likewise, old records from Sri Lanka are highly questionable and remain unconfirmed. Zebrafish have been introduced to California, Connecticut, Florida and New Mexico in the United States, presumably by deliberate release by aquarists or by escape from fish farms . The New Mexico population had been extirpated by 2003 and it

3298-497: Is linked to male infertility. The researchers cloned oestrogen-sensitive genes and injected them into the fertile eggs of zebrafish. The modified fish turned green if placed into water that was polluted by oestrogen. In 2015, researchers at Brown University discovered that 10% of zebrafish genes do not need to rely on the U2AF2 protein to initiate RNA splicing . These genes have the DNA base pairs AC and TG as repeated sequences at

3395-457: Is named Tbxt , and in humans it is named TBXT . Brachyury has been found in all bilaterian animals that have been screened, and is also present in the cnidaria . The mouse Tbxt gene was cloned and found to be a 436 amino acid embryonic nuclear transcription factor . The protein brachyury binds to the T-box through a region at its N-terminus. The encoded proteins of TBX5 and TBX4 play

3492-451: Is three months. A male must be present for ovulation and spawning to occur. Zebrafish are asynchronous spawners and under optimal conditions (such as food availability and favorable water parameters) can spawn successfully frequently, even on a daily basis. Females are able to spawn at intervals of two to three days, laying hundreds of eggs in each clutch . Upon release, embryonic development begins; in absence of sperm, growth stops after

3589-407: Is to reduce gene expression or modify splicing using Morpholino antisense technology. Morpholino oligonucleotides (MO) are stable, synthetic macromolecules that contain the same bases as DNA or RNA; by binding to complementary RNA sequences, they can reduce the expression of specific genes or block other processes from occurring on RNA. MO can be injected into one cell of an embryo after

3686-409: Is unclear if the others survive, as the last published records were decades ago. Elsewhere the species has been introduced to Colombia and Malaysia. Zebrafish typically inhabit moderately flowing to stagnant clear water of quite shallow depth in streams, canals, ditches, oxbow lakes , ponds and rice paddies . There is usually some vegetation, either submerged or overhanging from the banks, and

3783-414: Is very rapid, and its embryos are relatively large, robust, and transparent, and able to develop outside their mother. Furthermore, well-characterized mutant strains are readily available. Other advantages include the species' nearly constant size during early development, which enables simple staining techniques to be used, and the fact that its two-celled embryo can be fused into a single cell to create

3880-586: The Carp (including Grass Carp, Ctenopharyngodon idella ) and Milkfish ( Chanos chanos ) which are quite close, both being in the Cyprinidae . However it should also be noted that Danio consistently proves to be a useful model for mammals in many cases and there is dramatically more genetic distance between them than between Danio and any farmed fish. In a glucocorticoid receptor -defective mutant with reduced exploratory behavior , fluoxetine rescued

3977-474: The Drosophila genome has been performed using various techniques, including P element , Cre-loxP , and ΦC31 insertion. The most practiced method used thus far to insert transgenes into the Drosophila genome utilizes P elements. The transposable P elements, also known as transposons , are segments of bacterial DNA that are translocated into the genome, without the presence of a complementary sequence in

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4074-634: The Ministry of Science and Technology of China and the Chinese Academy of Sciences . The Zebrafish Information Network ( ZFIN ) provides up-to-date information about current known wild-type (WT) strains of D. rerio , some of which are listed below. Hybrids between different Danio species may be fertile: for example, between D. rerio and D. nigrofasciatus . D. rerio is a common and useful scientific model organism for studies of vertebrate development and gene function. Its use as

4171-432: The replication crisis in biomedical research. Genetic differences in wild-type lines among populations maintained at different research institutions have been demonstrated using both Single-nucleotide polymorphisms and microsatellite analysis. Due to their fast and short life cycles and relatively large clutch sizes, D. rerio or zebrafish are a useful model for genetic studies. A common reverse genetics technique

4268-410: The 32-cell stage, reducing gene expression in only cells descended from that cell. However, cells in the early embryo (less than 32 cells) are permeable to large molecules, allowing diffusion between cells. Guidelines for using Morpholinos in zebrafish describe appropriate control strategies. Morpholinos are commonly microinjected in 500pL directly into 1–2 cell stage zebrafish embryos. The morpholino

4365-494: The DNA had to be compatible for offspring to be able to reproduce. In the 1970 and 1980s, scientists passed this hurdle by inventing procedures for combining the DNA of two vastly different species with genetic engineering . The organisms produced by these procedures were termed transgenic. Transgenesis is the same as gene therapy in the sense that they both transform cells for a specific purpose. However, they are completely different in their purposes, as gene therapy aims to cure

4462-826: The South Himalayas , ranging from the Sutlej river basin in the Pakistan–India border region to the state of Arunachal Pradesh in northeast India. Its range is concentrated in the Ganges and Brahmaputra River basins, and the species was first described from Kosi River (lower Ganges basin) of India. Its range further south is more local, with scattered records from the Western and Eastern Ghats regions. It has frequently been said to occur in Myanmar (Burma), but this

4559-523: The United States could explain the frequency and distribution of transgenes in west-central Mexico, but not in the southeast. Also, 5.0% of corn seed lots in Mexican corn stocks expressed recombinant proteins despite the moratorium on GM crops. In 2011, transgenic cotton was found in Mexico among wild cotton, after 15 years of GMO cotton cultivation. Transgenic rapeseed Brassicus napus – hybridized with

4656-482: The United States). Transgene escape has been documented for GMO crops since 2001 with persistence and invasiveness. Transgenetic organisms pose ethical questions and may cause biosafety problems. The idea of shaping an organism to fit a specific need is not a new science. However, until the late 1900s farmers and scientists could breed new strains of a plant or organism only from closely related species because

4753-399: The absence of an immune system makes the use of patient derived xenografts possible. In January 2013, Japanese scientists genetically modified a transparent zebrafish specimen to produce a visible glow during periods of intense brain activity. In January 2007, Chinese researchers at Fudan University genetically modified zebrafish to detect oestrogen pollution in lakes and rivers, which

4850-486: The animal's vulnerability to cancer. Cancer researchers utilize oncomice to study the profiles of different cancers in order to apply this knowledge to human studies. Multiple studies have been conducted concerning transgenesis in Drosophila melanogaster , the fruit fly. This organism has been a helpful genetic model for over 100 years, due to its well-understood developmental pattern. The transfer of transgenes into

4947-434: The artificial interaction produced between LEF1 and Catenin beta-1 /β-catenin/ CTNNB1 . Dorsky et al. 2002 investigated the developmental role of Wnt by transgenically expressing a Lef1/β-catenin reporter. There are well-established protocols for editing zebrafish genes using CRISPR-Cas9 and this tool has been used to generate genetically modified models. In 2008, researchers at Boston Children's Hospital developed

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5044-434: The bottom is sandy, muddy or silty, often mixed with pebbles or gravel. In surveys of zebrafish locations throughout much of its Bangladeshi and Indian distribution, the water had a near-neutral to somewhat basic pH and mostly ranged from 16.5 to 34 °C (61.7–93.2 °F) in temperature. One unusually cold site was only 12.3 °C (54.1 °F) and another unusually warm site was 38.6 °C (101.5 °F), but

5141-783: The damaged heart are sensed by ventricular endothelial cells and their associated cardiac cilia by way of the mechanosensitive ion channel TRPV4 , subsequently facilitating the Notch signaling pathway via KLF2 and activating various downstream effectors such as BMP-2 and HER2/neu . In 2011, the British Heart Foundation ran an advertising campaign publicising its intention to study the applicability of this ability to humans, stating that it aimed to raise £50 million in research funding. Zebrafish have also been found to regenerate photoreceptor cells and retinal neurons following injury, which has been shown to be mediated by

5238-424: The dedifferentiation and proliferation of Müller glia . Researchers frequently amputate the dorsal and ventral tail fins and analyze their regrowth to test for mutations. It has been found that histone demethylation occurs at the site of the amputation, switching the zebrafish's cells to an "active", regenerative, stem cell-like state. In 2012, Australian scientists published a study revealing that zebrafish use

5335-492: The detrimental effects of inbreeding depression . Inbreeding depression is predominantly caused by the homozygous expression of recessive deleterious alleles. For zebrafish, inbreeding depression might be expected to be more severe in stressful environments, including those caused by anthropogenic pollution . Exposure of zebrafish to environmental stress induced by the chemical clotrimazole, an imidazole fungicide used in agriculture and in veterinary and human medicine, amplified

5432-487: The developing limb bud, which specify the orientation growth of the developing limb. Together, TBX5 and TBX4 play a role in patterning the soft tissues (muscles and tendons) of the musculoskeletal system. In humans, and some other animals, defects in the TBX5 gene expression are responsible for Holt–Oram syndrome , which is characterized by at least one abnormal wrist bone . Other arm bones are almost always affected, though

5529-448: The effects of inbreeding on key reproductive traits. Embryo viability was significantly reduced in inbred exposed fish and there was a tendency for inbred males to sire fewer offspring. Zebrafish are common models for research into fish farming , including pathogens and parasites causing yield loss or spreading to adjacent wild populations. This usefulness is less than it might be due to Danio ' s taxonomic distance from

5626-480: The end of the caudal fin . Its shape is fusiform and laterally compressed, with its mouth directed upwards. The male is torpedo -shaped, with gold stripes between the blue stripes; the female has a larger, whitish belly and silver stripes instead of gold. Adult females exhibit a small genital papilla in front of the anal fin origin. The zebrafish can reach up to 4–5 cm (1.6–2.0 in) in length, although they typically are 1.8–3.7 cm (0.7–1.5 in) in

5723-457: The ends of each intron . On the 3'ss (3' splicing site), the base pairs adenine and cytosine alternate and repeat, and on the 5'ss (5' splicing site), their complements thymine and guanine alternate and repeat as well. They found that there was less reliance on U2AF2 protein than in humans, in which the protein is required for the splicing process to occur. The pattern of repeating base pairs around introns that alters RNA secondary structure

5820-503: The fields of developmental biology , oncology , toxicology , reproductive studies, teratology , genetics , neurobiology , environmental sciences , stem cell research, regenerative medicine , muscular dystrophies and evolutionary theory . As a model biological system, the zebrafish possesses numerous advantages for scientists. Its genome has been fully sequenced , and it has well-understood, easily observable and testable developmental behaviors. Its embryonic development

5917-443: The first few cell divisions. Fertilized eggs almost immediately become transparent, a characteristic that makes D. rerio a convenient research model species . Sex determination of common laboratory strains was shown to be a complex genetic trait, rather than to follow a simple ZW or XY system. The zebrafish embryo develops rapidly, with precursors to all major organs appearing within 36 hours of fertilization. The embryo begins as

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6014-476: The first few days (72 h panel). After a few months, the adult fish reaches reproductive maturity (bottom panel). To encourage the fish to spawn, some researchers use a fish tank with a sliding bottom insert, which reduces the depth of the pool to simulate the shore of a river. Zebrafish spawn best in the morning due to their Circadian rhythms . Researchers have been able to collect 10,000 embryos in 10 minutes using this method. In particular, one pair of adult fish

6111-409: The first species to be sold as GloFish (fluorescent colored fish). In late 2003, transgenic zebrafish that express green , red, and yellow fluorescent proteins became commercially available in the United States. The fluorescent strains are trade-named GloFish ; other cultivated varieties include "golden", "sandy", "longfin" and "leopard". The leopard danio, previously known as Danio frankei ,

6208-511: The genus Brachydanio , of the family Cyprinidae . It has a sister-group relationship with Danio aesculapii . Zebrafish are also closely related to the genus Devario , as demonstrated by a phylogenetic tree of close species. The zebrafish is native to freshwater habitats in South Asia where it is found in India, Pakistan, Bangladesh, Nepal and Bhutan. The northern limit is in

6305-634: The heavy strand. In between a grouping of five tRNA genes, a sequence resembling vertebrate origin of light strand replication is found. It is difficult to draw evolutionary conclusions because it is difficult to determine whether base pair changes have adaptive significance via comparisons with other vertebrates' nucleotide sequences. T-boxes and homeoboxes are vital in Danio similarly to other vertebrates. The Bruce et al. team are known for this area, and in Bruce et al. 2003 & Bruce et al. 2005 uncover

6402-415: The host's genome. P elements are administered in pairs of two, which flank the DNA insertion region of interest. Additionally, P elements often consist of two plasmid components, one known as the P element transposase and the other, the P transposon backbone. The transposase plasmid portion drives the transposition of the P transposon backbone, containing the transgene of interest and often a marker, between

6499-428: The medical field. Scientists are focusing on the use of transgenes to study the function of the human genome in order to better understand disease, adapting animal organs for transplantation into humans, and the production of pharmaceutical products such as insulin , growth hormone , and blood anti-clotting factors from the milk of transgenic cows. As of 2004 there were five thousand known genetic diseases , and

6596-503: The microinjection of the bacteriophage ΦC31 integrase, which shows improved transgene insertion of large DNA fragments that are unable to be transposed by P elements alone. This method involves the recombination between an attachment (attP) site in the phage and an attachment site in the bacterial host genome (attB). Compared to usual P element transgene insertion methods, ΦC31 integrates the entire transgene vector, including bacterial sequences and antibiotic resistance genes. Unfortunately,

6693-702: The mid-1990s. There is agreement that escape of transgenes is inevitable, even "some proof that it is happening". Up until 2008 there were few documented cases. Corn sampled in 2000 from the Sierra Juarez, Oaxaca , Mexico contained a transgenic 35S promoter, while a large sample taken by a different method from the same region in 2003 and 2004 did not. A sample from another region from 2002 also did not, but directed samples taken in 2004 did, suggesting transgene persistence or re-introduction. A 2009 study found recombinant proteins in 3.1% and 1.8% of samples, most commonly in southeast Mexico. Seed and grain import from

6790-433: The milk of goats. Another agricultural application is to selectively breed animals, which are resistant to diseases or animals for biopharmaceutical production. The application of transgenes is a rapidly growing area of molecular biology . As of 2005 it was predicted that in the next two decades, 300,000 lines of transgenic mice will be generated. Researchers have identified many applications for transgenes, particularly in

6887-452: The most common animal model for transgenic research. Transgenic mice are currently being used to study a variety of diseases including cancer, obesity, heart disease, arthritis, anxiety, and Parkinson's disease. The two most common types of genetically modified mice are knockout mice and oncomice . Knockout mice are a type of mouse model that uses transgenic insertion to disrupt an existing gene's expression. In order to create knockout mice,

6984-709: The most common aquaculture species. Because the most common are salmonids and cod in the Protacanthopterygii and sea bass , sea bream , tilapia , and flatfish , in the Percomorpha , zebrafish results may not be perfectly applicable. Various other models – Goldfish ( Carassius auratus ), Medaka ( Oryzias latipes ), Stickleback ( Gasterosteus aculeatus ), Roach ( Rutilus rutilus ), Pufferfish ( Takifugu rubripes ), Swordtail ( Xiphophorus hellerii ) – are less used normally but would be closer to particular target species. The only exception are

7081-460: The mother – will prevent initiation of the mesoderm or endoderm development processes in this species.) In 1999, the nacre mutation was identified in the zebrafish ortholog of the mammalian MITF transcription factor. Mutations in human MITF result in eye defects and loss of pigment, a type of Waardenburg Syndrome . In December 2005, a study of the golden strain identified the gene responsible for its unusual pigmentation as SLC24A5 ,

7178-459: The newly fertilized egg. The first transgenic animals were only intended for genetic research to study the specific function of a gene, and by 2003, thousands of genes had been studied. A variety of transgenic plants have been designed for agriculture to produce genetically modified crops , such as corn, soybean, rapeseed oil, cotton, rice and more. As of 2012 , these GMO crops were planted on 170 million hectares globally. One example of

7275-467: The normal exploratory behavior. This demonstrates relationships between glucocorticoids, fluoxetine, and exploration in this fish. Zebrafish have been used as a model for studying DNA repair pathways. Embryos of externally fertilized fish species, such as zebrafish during their development, are directly exposed to environmental conditions such as pollutants and reactive oxygen species that may cause damage to their DNA . To cope with such DNA damages,

7372-428: The opportunity, adults eat hatchlings, which may be protected by separating the two groups with a net, breeding box or separate tank. In captivity, zebrafish live approximately forty-two months. Some captive zebrafish can develop a curved spine. They can range from a few centimeters to a few inches, and provide movement in a freshwater fish tank. The zebra danio was also used to make genetically modified fish and were

7469-528: The potential to treat these diseases using transgenic animals is, perhaps, one of the most promising applications of transgenes. There is a potential to use human gene therapy to replace a mutated gene with an unmutated copy of a transgene in order to treat the genetic disorder. This can be done through the use of Cre-Lox or knockout . Moreover, genetic disorders are being studied through the use of transgenic mice, pigs, rabbits, and rats. Transgenic rabbits have been created to study inherited cardiac arrhythmias, as

7566-514: The presence of these additional insertions has been found to affect the level and reproducibility of transgene expression. One agricultural application is to selectively breed animals for particular traits: Transgenic cattle with an increased muscle phenotype has been produced by overexpressing a short hairpin RNA with homology to the myostatin mRNA using RNA interference . Transgenes are being used to produce milk with high levels of proteins or silk from

7663-429: The process, such as Wnt signaling and Fibroblast growth factor . In probing disorders of the nervous system, including neurodegenerative diseases, movement disorders, psychiatric disorders and deafness, researchers are using the zebrafish to understand how the genetic defects underlying these conditions cause functional abnormalities in the human brain, spinal cord and sensory organs. Researchers have also studied

7760-450: The production of β-carotene . The product was a transgenic rice species rich in vitamin A, called golden rice . Little is known about the impact of golden rice on xerophthalmia because anti-GMO campaigns have prevented the full commercial release of golden rice into agricultural systems in need. The escape of genetically-engineered plant genes via hybridization with wild relatives was first discussed and examined in Mexico and Europe in

7857-425: The rabbit heart markedly better resembles the human heart as compared to the mouse. More recently, scientists have also begun using transgenic goats to study genetic disorders related to fertility . Transgenes may be used for xenotransplantation from pig organs. Through the study of xeno-organ rejection, it was found that an acute rejection of the transplanted organ occurs upon the organ's contact with blood from

7954-481: The rate of industrial reactions. Transgene use in humans is currently fraught with issues. Transformation of genes into human cells has not been perfected yet. The most famous example of this involved certain patients developing T-cell leukemia after being treated for X-linked severe combined immunodeficiency (X-SCID). This was attributed to the close proximity of the inserted gene to the LMO2 promoter, which controls

8051-509: The recipient due to the recognition of foreign antibodies on endothelial cells of the transplanted organ. Scientists have identified the antigen in pigs that causes this reaction, and therefore are able to transplant the organ without immediate rejection by removal of the antigen. However, the antigen begins to be expressed later on, and rejection occurs. Therefore, further research is being conducted. Transgenic microorganisms capable of producing catalytic proteins or enzymes which increase

8148-584: The recommended feeding rate decreases to about 6–8% of their BW per day, with a focus on high-quality dry feeds that meet their protein and energy needs. Upon reaching adulthood (over 90 dpf), zebrafish typically require a feeding rate of around 5% of their BW per day. Throughout these stages, it is essential to adjust the particle size of the feed: less than 100 μm for newly hatched larvae, 100–200 μm for those between 16 and 30 dpf, and larger particles for juveniles and adults. This structured approach to feeding not only supports optimal growth and health but also enhances

8245-551: The reliability of experimental outcomes in research settings Zebrafish are hardy fish and considered good for beginner aquarists. Their enduring popularity can be attributed to their playful disposition, as well as their rapid breeding, aesthetics, cheap price and broad availability. They also do well in schools or shoals of six or more, and interact well with other fish species in the aquarium. However, they are susceptible to Oodinium or velvet disease, microsporidia ( Pseudoloma neurophilia ), and Mycobacterium species. Given

8342-457: The role of two of these elements in oocytes of this species. By interfering via a dominant nonfunctional allele and a morpholino they find the T-box transcription activator Eomesodermin and its target mtx2 – a transcription factor – are vital to epiboly . (In Bruce et al. 2003 they failed to support the possibility that Eomesodermin behaves like Vegt . Neither they nor anyone else has been able to locate any mutation which – in

8439-539: The severity can vary widely, from complete absence of a bone, to only a reduction in bone length. Seventy-five percent of affected individuals also have heart defects , most often there is no separation between the left and right ventricle of the heart . TBX3 is associated with ulnar–mammary syndrome in humans, but is also responsible for the presence or absence of dun color in horses, and has no deleterious effects whether expressed or not. Genes encoding T-box proteins include: This protein -related article

8536-464: The transgenic organism's genetic code. In general, the DNA is incorporated into the organism's germ line . For example, in higher vertebrates this can be accomplished by injecting the foreign DNA into the nucleus of a fertilized ovum . This technique is routinely used to introduce human disease genes or other genes of interest into strains of laboratory mice to study the function or pathology involved with that particular gene. The construction of

8633-489: The two terminal sites of the transposon. Success of this insertion results in the nonreversible addition of the transgene of interest into the genome. While this method has been proven effective, the insertion sites of the P elements are often uncontrollable, resulting in an unfavorable, random insertion of the transgene into the Drosophila genome. To improve the location and precision of the transgenic process, an enzyme known as Cre has been introduced. Cre has proven to be

8730-462: The very first transmutations were performed by microinjection of DNA directly into cells. Scientists were able to develop other methods to perform the transformations, such as incorporating transgenes into retroviruses and then infecting cells; using electroinfusion, which takes advantage of an electric current to pass foreign DNA through the cell wall; biolistics , which is the procedure of shooting DNA bullets into cells; and also delivering DNA into

8827-442: The wild form gene pool. Transgenic creeping bentgrass , engineered to be glyphosate -tolerant as "one of the first wind-pollinated, perennial, and highly outcrossing transgenic crops", was planted in 2003 as part of a large (about 160 ha) field trial in central Oregon near Madras, Oregon . In 2004, its pollen was found to have reached wild growing bentgrass populations up to 14 kilometres away. Cross-pollinating Agrostis gigantea

8924-454: The wild with some variations depending on location. Its lifespan in captivity is around two to three years, although in ideal conditions, this may be extended to over five years. In the wild it is typically an annual species. In 2015, a study was published about zebrafishes' capacity for episodic memory . The individuals showed a capacity to remember context with respect to objects, locations and occasions (what, when, where). Episodic memory

9021-460: The zebrafish reference genome revealed over 5 million single nucleotide variations and over 1.6 million insertion deletion variations. The zebrafish reference genome sequence of 1.4GB and over 26,000 protein coding genes was published by Kerstin Howe et al. in 2013. In October 2001, researchers from the University of Oklahoma published D. rerio's complete mitochondrial DNA sequence. Its length

9118-414: The zebrafish still appeared healthy. The unusually cold temperature was at one of the highest known zebrafish locations at 1,576 m (5,171 ft) above sea level, although the species has been recorded to 1,795 m (5,889 ft). The zebrafish is named for the five uniform, pigmented, horizontal, blue stripes on the side of the body, which are reminiscent of a zebra's stripes, and which extend to

9215-473: The zebrafish to gain new insights into the complexities of human musculoskeletal diseases, such as muscular dystrophy . Another focus of zebrafish research is to understand how a gene called Hedgehog , a biological signal that underlies a number of human cancers, controls cell growth. Inbred strains and traditional outbred stocks have not been developed for laboratory zebrafish, and the genetic variability of wild-type lines among institutions may contribute to

9312-464: Was even found at a distance of 21 kilometres. The grower, Scotts Company could not remove all genetically engineered plants, and in 2007, the U.S. Department of Agriculture fined Scotts $ 500,000 for noncompliance with regulations. The long-term monitoring and controlling of a particular transgene has been shown not to be feasible. The European Food Safety Authority published a guidance for risk assessment in 2010. Genetically modified mice are

9409-467: Was found in other teleosts , but not in tetrapods . This indicates that an evolutionary change in tetrapods may have led to humans relying on the U2AF2 protein for RNA splicing while these genes in zebrafish undergo splicing regardless of the presence of the protein. D. rerio has three transferrins , all of which cluster closely with other vertebrates . When close relatives mate, progeny may exhibit

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