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Gene Drive
A gene drive is a natural process and technology of genetic engineering that propagates a particular suite of genes throughout a population by altering the probability that a specific allele will be transmitted to offspring (instead of the Mendelian 50% probability). Gene drives can arise through a variety of mechanisms. They have been proposed to provide an effective means of genetically modifying specific populations and entire species. The technique can employ adding, deleting, disrupting, or modifying genes. Proposed applications include exterminating insects that carry pathogens (notably mosquitoes that transmit malaria, dengue, and zika pathogens), controlling invasive species, or eliminating herbicide or pesticide resistance. As with any potentially powerful technique, gene drives can be misused in a variety of ways or induce unintended consequences. For example, a gene drive intended to affect only a local population might spread across an entire species. Gene driv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromosome
A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most important of these proteins are the histones. Aided by chaperone proteins, the histones bind to and condense the DNA molecule to maintain its integrity. These eukaryotic chromosomes display a complex three-dimensional structure that has a significant role in transcriptional regulation. Normally, chromosomes are visible under a light microscope only during the metaphase of cell division, where all chromosomes are aligned in the center of the cell in their condensed form. Before this stage occurs, each chromosome is duplicated ( S phase), and the two copies are joined by a centromere—resulting in either an X-shaped structure if the centromere is located equatorially, or a two-armed structure if the centromere is located distally; the jo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Nucleus
The cell nucleus (; : nuclei) is a membrane-bound organelle found in eukaryote, eukaryotic cell (biology), cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have #Anucleated_cells, no nuclei, and a few others including osteoclasts have Multinucleate, many. The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and isolates its contents from the cellular cytoplasm; and the nuclear matrix, a network within the nucleus that adds mechanical support. The cell nucleus contains nearly all of the cell's genome. Nuclear DNA is often organized into multiple chromosomes – long strands of DNA dotted with various proteins, such as histones, that protect and organize the DNA. The genes within these chromosomes are Nuclear organization, structured in such a way to promote cell function. The nucleus maintains the integrity of genes and controls the activities of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology (biology)
In biology, homology is similarity in anatomical structures or genes between organisms of different taxa due to shared ancestry, ''regardless'' of current functional differences. Evolutionary biology explains homologous structures as retained heredity from a common descent, common ancestor after having been subjected to adaptation (biology), adaptive modifications for different purposes as the result of natural selection. The term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was later explained by Charles Darwin's theory of evolution in 1859, but had been observed before this from Aristotle's biology onwards, and it was explicitly analysed by Pierre Belon in 1555. A common example of homologous structures is the forelimbs of vertebrates, where the bat wing development, wings of bats and origin of avian flight, birds, the arms of primates, the front flipper (anatomy), flippers of whales, and the forelegs of quadrupedalis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Double-strand Break
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. A weakened capacity for DNA repair is a risk factor for the development of cancer. DNA is constantly modified in cells, by internal metabolic by-products, and by external ionizing radiation, ultraviolet light, and medicines, resulting in spontaneous DNA damage involving tens of thousands of individual molecular lesions per cell per day. DNA modifications can also be programmed. Molecular lesions can cause structural damage to the DNA molecule, and can alter or eliminate the cell's ability for transcription and gene expression. Other lesions may induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells following mitosis. Consequently, DNA repair as part of the DNA damage response (DDR) is constantly active. When normal repair processes fail, including apoptosis, irreparable DNA damage may occur, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription Activator-like Effector Nuclease
Transcription activator-like effector nucleases (TALEN) are restriction enzymes that can be engineered to cut specific sequences of DNA. They are made by fusing a TAL effector DNA-binding domain to a DNA cleavage domain (a nuclease which cuts DNA strands). Transcription activator-like effectors (TALEs) can be engineered to bind to practically any desired DNA sequence, so when combined with a nuclease, DNA can be cut at specific locations. The restriction enzymes can be introduced into cells, for use in Genome editing, gene editing or for genome editing ''in situ'', a technique known as genome editing with engineered nucleases. Alongside zinc finger nucleases and CRISPR, CRISPR/Cas9, TALEN is a prominent tool in the field of genome editing. TALE DNA-binding domain TAL effectors are proteins that are secreted by ''Xanthomonas'' bacteria via their type three secretion system, type III secretion system when they plant pathology, infect plants. The DNA binding domain contains a repeat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zinc Finger
A zinc finger is a small protein structural motif that is characterized by the coordination of one or more zinc ions (Zn2+) which stabilizes the fold. The term ''zinc finger'' was originally coined to describe the finger-like appearance of a hypothesized structure from the African clawed frog (''Xenopus laevis'') transcription factor IIIA. However, it has been found to encompass a wide variety of differing protein structures in eukaryotic cells. '' Xenopus laevis'' TFIIIA was originally demonstrated to contain zinc and require the metal for function in 1983, the first such reported zinc requirement for a gene regulatory protein followed soon thereafter by the Krüppel factor in ''Drosophila''. It often appears as a metal-binding domain in multi-domain proteins. Proteins that contain zinc fingers (zinc finger proteins) are classified into several different structural families. Unlike many other clearly defined supersecondary structures such as Greek keys or β hairpins, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guide RNA
Guide RNA (gRNA) or single guide RNA (sgRNA) is a short sequence of RNA that functions as a guide for the Cas9-endonuclease or other Cas-proteins that cut the double-stranded DNA and thereby can be used for gene editing. In bacteria and archaea, gRNAs are a part of the CRISPR-Cas system that serves as an adaptive immune defense that protects the organism from viruses. Here the short gRNAs serve as detectors of foreign DNA and direct the Cas-enzymes that degrades the foreign nucleic acid. History The RNA editing guide RNA was discovered in 1990 by B. Blum, N. Bakalara, and L. Simpson through Northern Blot Hybridization in the mitochondrial maxicircle DNA of the eukaryotic parasite Leishmania tarentolae. Subsequent research throughout the mid-2000s and the following years explored the structure and function of gRNA and the CRISPR-Cas system. A significant breakthrough occurred in 2012 when it was discovered that gRNA could guide the Cas9 endonuclease to introduce target-specific cu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cas12a
Cas12a (CRISPR-associated protein 12a, previously known as Cpf1) is an RNA-guided endonuclease-exonuclease that forms an essential component of the CRISPR systems found in some bacteria and archaea. In its natural context, Cas12a targets and destroys the genetic material of viruses and other foreign mobile genetic elements, thereby protecting the host cell from infection. Like other Cas enzymes, Cas12a binds to a "guide" RNA (termed a crRNA, or CRISPR RNA) which targets it to a DNA sequence in a specific and programmable matter. In the host organism, the crRNA contains a constant region that is recognized by the Cas12a protein and a "spacer" region that is complementary to a piece of foreign nucleic acid (e.g. a portion of a phage genome) that previously infected the cell. As with Cas9 and other Cas proteins, the programmable DNA-targeting activity of Cas12a makes it a useful tool for biotechnology and biological research applications. By modifying the spacer sequence in the crR ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cas9
Cas9 (CRISPR associated protein 9, formerly called Cas5, Csn1, or Csx12) is a 160 dalton (unit), kilodalton protein which plays a vital role in the immunological defense of certain bacteria against DNA viruses and plasmids, and is heavily utilized in genetic engineering applications. Its main function is to cut DNA and thereby alter a cell's genome. The CRISPR gene editing, CRISPR-Cas9 genome editing technique was a significant contributor to the Nobel Prize in Chemistry in 2020 being awarded to Emmanuelle Charpentier and Jennifer Doudna. More technically, Cas9 is a RNA-guided DNA endonuclease enzyme associated with the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) adaptive immune system in ''Streptococcus pyogenes''. ''S. pyogenes'' utilizes CRISPR to memorize and Cas9 to later interrogate and cleave foreign DNA, such as invading bacteriophage DNA or plasmid DNA. Cas9 performs this interrogation by unwinding foreign DNA and checking for sites complementary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intein
Protein splicing is an intramolecular reaction of a particular protein in which an internal protein segment (called an intein) is removed from a precursor protein with a ligation of C-terminal and N-terminal external proteins (called exteins) on both sides. The splicing junction of the precursor protein is mainly a cysteine or a serine, which are amino acids containing a nucleophilic side chain. The protein splicing reactions which are known now do not require exogenous cofactors or energy sources such as adenosine triphosphate (ATP) or guanosine triphosphate (GTP). Normally, splicing is associated only with pre-mRNA splicing. This precursor protein contains three segments—an N-extein followed by the intein followed by a C-extein. After splicing has taken place, the resulting protein contains the N-extein linked to the C-extein; this splicing product is also termed an extein. History The first intein was discovered in 1988 through sequence comparison between the ''Neurospora cr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homing Endonuclease
The homing endonucleases are a collection of endonucleases encoded either as freestanding genes within introns, as fusions with host proteins, or as self-splicing inteins. They catalyze the hydrolysis of genomic DNA within the cells that synthesize them, but do so at very few, or even singular, locations. Repair of the hydrolyzed DNA by the host cell frequently results in the gene encoding the homing endonuclease having been copied into the cleavage site, hence the term 'homing' to describe the movement of these genes. Homing endonucleases can thereby transmit their genes Horizontal gene transfer, horizontally within a host population, increasing their allele frequency at greater than Mendelian rates. Origin and mechanism Although the origin and function of homing endonucleases is still being researched, the most established hypothesis considers them as selfish DNA, selfish genetic elements, similar to transposons, because they facilitate the perpetuation of the genetic elements ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
