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Topologically Associating Domain
A topologically associating domain (TAD) is a self-interacting genomic region, meaning that DNA sequences within a TAD physically interact with each other more frequently than with sequences outside the TAD. The median size of a TAD in mouse cells is 880 kb, and they have similar sizes in non-mammalian species. Boundaries at both side of these domains are conserved between different mammalian cell types and even across species and are highly enriched with CCCTC-binding factor (CTCF) and cohesin. In addition, some types of genes (such as transfer RNA genes and housekeeping genes) appear near TAD boundaries more often than would be expected by chance. The functions of TADs are not fully understood and are still a matter of debate. Most of the studies indicate TADs regulate gene expression by limiting the enhancer- promoter interaction to each TAD, however, a recent study uncouples TAD organization and gene expression. Disruption of TAD boundaries are found to be associated with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structural Organization Of Chromatin
A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as biological organisms, minerals and chemicals. Abstract structures include data structures in computer science and musical form. Types of structure include a hierarchy (a cascade of one-to-many relationships), a network featuring many-to-many links, or a lattice featuring connections between components that are neighbors in space. Load-bearing Buildings, aircraft, skeletons, anthills, beaver dams, bridges and salt domes are all examples of load-bearing structures. The results of construction are divided into buildings and non-building structures, and make up the infrastructure of a human society. Built structures are broadly divided by their varying design approaches and standards, into categories including building structures, arc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mouse
A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus''). Mice are also popular as pets. In some places, certain kinds of field mice are locally common. They are known to invade homes for food and shelter. Mice are typically distinguished from rats by their size. Generally, when a muroid rodent is discovered, its common name includes the term ''mouse'' if it is smaller, or ''rat'' if it is larger. The common terms ''rat'' and ''mouse'' are not taxonomically specific. Typical mice are classified in the genus ''Mus'', but the term ''mouse'' is not confined to members of ''Mus'' and can also apply to species from other genera such as the deer mouse, ''Peromyscus''. Domestic mice sold as pets often differ substantially in size from the common house mouse. This is attributable to breeding a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Post-translational Modification
Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribosomes translating mRNA into polypeptide chains, which may then undergo PTM to form the mature protein product. PTMs are important components in cell signaling, as for example when prohormones are converted to hormones. Post-translational modifications can occur on the amino acid side chains or at the protein's C- or N- termini. They can extend the chemical repertoire of the 20 standard amino acids by modifying an existing functional group or introducing a new one such as phosphate. Phosphorylation is a highly effective mechanism for regulating the activity of enzymes and is the most common post-translational modification. Many eukaryotic and prokaryotic proteins also have carbohydrate molecules attached to them in a process called gly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
H3K27me3
H3K27me3 is an epigenetic modification to the DNA packaging protein Histone H3. It is a mark that indicates the tri-methylation of lysine 27 on histone H3 protein. This tri-methylation is associated with the downregulation of nearby genes via the formation of heterochromatic regions. Nomenclature H3K27me3 indicates trimethylation of lysine 27 on histone H3 protein subunit: Lysine methylation This diagram shows the progressive methylation of a lysine residue. The tri-methylation denotes the methylation present in H3K27me3. Understanding histone modifications The genomic DNA of eukaryotic cells is wrapped around special protein molecules known as Histones. The complexes formed by the looping of the DNA are known as Chromatin. The basic structural unit of chromatin is the Nucleosome: this consists of the core octamer of histones (H2A, H2B, H3 and H4) as well as a linker histone and about 180 base pairs of DNA. These core histones are rich in lysine and arginine residues. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Histone H3
Histone H3 is one of the five main histones involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and a long N-terminal tail, H3 is involved with the structure of the nucleosomes of the 'beads on a string' structure. Histone proteins are highly post-translationally modified however Histone H3 is the most extensively modified of the five histones. The term "Histone H3" alone is purposely ambiguous in that it does not distinguish between sequence variants or modification state. Histone H3 is an important protein in the emerging field of epigenetics, where its sequence variants and variable modification states are thought to play a role in the dynamic and long term regulation of genes. Epigenetics and post-translational modifications The N-terminus of H3 protrudes from the globular nucleosome core and is susceptible to post-translational modification that influence cellular processes. These modifications include the covalent attachment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Histone Methylation
Histone methylation is a process by which methyl groups are transferred to amino acids of histone proteins that make up nucleosomes, which the DNA double helix wraps around to form chromosomes. Methylation of histones can either increase or decrease transcription of genes, depending on which amino acids in the histones are methylated, and how many methyl groups are attached. Methylation events that weaken chemical attractions between histone tails and DNA increase transcription because they enable the DNA to uncoil from nucleosomes so that transcription factor proteins and RNA polymerase can access the DNA. This process is critical for the regulation of gene expression that allows different cells to express different genes. Function Histone methylation, as a mechanism for modifying chromatin structure is associated with stimulation of neural pathways known to be important for formation of long-term memories and learning. Animal models have shown methylation and other epigenetic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Membrane
The nuclear envelope, also known as the nuclear membrane, is made up of two lipid bilayer membranes that in eukaryotic cells surround the nucleus, which encloses the genetic material. The nuclear envelope consists of two lipid bilayer membranes: an inner nuclear membrane and an outer nuclear membrane. The space between the membranes is called the perinuclear space. It is usually about 10–50 nm wide. The outer nuclear membrane is continuous with the endoplasmic reticulum membrane. The nuclear envelope has many nuclear pores that allow materials to move between the cytosol and the nucleus. Intermediate filament proteins called lamins form a structure called the nuclear lamina on the inner aspect of the inner nuclear membrane and give structural support to the nucleus. Structure The nuclear envelope is made up of two lipid bilayer membranes, an inner nuclear membrane and an outer nuclear membrane. These membranes are connected to each other by nuclear pores. Two sets of i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lamina Associated Domains, LAD
Lamina may refer to: Science and technology * Planar lamina, a two-dimensional planar closed surface with mass and density, in mathematics * Laminar flow, (or streamline flow) occurs when a fluid flows in parallel layers, with no disruption between the layers * Lamina (algae), a structure in seaweeds * Lamina (anatomy), with several meanings * Lamina (leaf), the flat part of a leaf, an organ of a plant * Lamina, the largest petal of a floret in an aster family flowerhead: see * ''Lamina'' (spider), a genus in the family Toxopidae * Lamina (neuropil), the most peripheral neuropil of the insect visual system *Nuclear lamina The nuclear lamina is a dense (~30 to 100 nm thick) fibrillar network inside the nucleus of eukaryote cells. It is composed of intermediate filaments and membrane associated proteins. Besides providing mechanical support, the nuclear lamina ..., another structure of a living cell *Basal lamina, a structure of a living cell *Lamina propria, the conne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insulated Neighborhood
In mammalian biology, insulated neighborhoods are chromosomal loop structures formed by the physical interaction of two DNA loci bound by the transcription factor CTCF and co-occupied by cohesin. Insulated neighborhoods are thought to be structural and functional units of gene control because their integrity is important for normal gene regulation. Current evidence suggests that these structures form the mechanistic underpinnings of higher-order chromosome structures, including topologically associating domains (TADs). Insulated neighborhoods are functionally important in understanding gene regulation in normal cells and dysregulated gene expression in disease. Enhancer-gene targeting Mammalian gene transcription is generally controlled by enhancers. Enhancers can regulate transcription of genes at large distances by looping to physically contact their target genes. This property of enhancers makes it difficult to identify an enhancer’s target gene(s). Insulators, another ty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polydactyly
Polydactyly or polydactylism (), also known as hyperdactyly, is an anomaly in humans and animals resulting in supernumerary fingers and/or toes. Polydactyly is the opposite of oligodactyly (fewer fingers or toes). Signs and symptoms In humans/animals this condition can present itself on one or both hands or feet. The extra digit is usually a small piece of soft tissue that can be removed. Occasionally it contains bone without joints; rarely it may be a complete functioning digit. The extra digit is most common on the ulnar (little finger) side of the hand, less common on the radial ( thumb) side, and very rarely within the middle three digits. These are respectively known as postaxial (little finger), preaxial (thumb), and central (ring, middle, index fingers) polydactyly. The extra digit is most commonly an abnormal fork in an existing digit, or it may rarely originate at the wrist as a normal digit does. The incidence of congenital deformities in newborns is approximately 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CRISPR
CRISPR () (an acronym for clustered regularly interspaced short palindromic repeats) is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea. These sequences are derived from DNA fragments of bacteriophages that had previously infected the prokaryote. They are used to detect and destroy DNA from similar bacteriophages during subsequent infections. Hence these sequences play a key role in the antiviral (i.e. anti-phage) defense system of prokaryotes and provide a form of acquired immunity. CRISPR is found in approximately 50% of sequenced bacterial genomes and nearly 90% of sequenced archaea. Cas9 (or "CRISPR-associated protein 9") is an enzyme that uses CRISPR sequences as a guide to recognize and cleave specific strands of DNA that are complementary to the CRISPR sequence. Cas9 enzymes together with CRISPR sequences form the basis of a technology known as CRISPR-Cas9 that can be used to edit genes within organisms. This editi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enhancer (genetics)
In genetics, an enhancer is a short (50–1500 bp) region of DNA that can be bound by proteins ( activators) to increase the likelihood that transcription of a particular gene will occur. These proteins are usually referred to as transcription factors. Enhancers are ''cis''-acting. They can be located up to 1 Mbp (1,000,000 bp) away from the gene, upstream or downstream from the start site. There are hundreds of thousands of enhancers in the human genome. They are found in both prokaryotes and eukaryotes. The first discovery of a eukaryotic enhancer was in the immunoglobulin heavy chain gene in 1983. This enhancer, located in the large intron, provided an explanation for the transcriptional activation of rearranged Vh gene promoters while unrearranged Vh promoters remained inactive. Locations In eukaryotic cells the structure of the chromatin complex of DNA is folded in a way that functionally mimics the supercoiled state characteristic of prokaryotic DNA, so although the e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
