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Karenia (dinoflagellate)
''Karenia'' is a genus that consists of unicellular, photosynthetic, planktonic organisms found in marine environments. The genus currently consists of 12 described species. They are best known for their dense toxic algal blooms and red tides that cause considerable ecological and economical damage; some ''Karenia'' species cause severe animal mortality. One species, ''Karenia brevis'', is known to cause respiratory distress and neurotoxic shellfish poisoning (NSP) in humans. Taxonomy The genus ''Karenia'' is named for Dr. Karen Steidinger for her exceptional contributions to dinoflagellate research. She has spent many decades researching ''Karenia brevis''. 12 species have been described in the genus ''Karenia'' thus far: * ''Karenia asterichroma'' * ''Karenia bicuneiformis'' * ''Karenia brevis'' * ''Karenia brevisulcata'' * ''Karenia concordia'' * ''Karenia cristata'' * ''Karenia digitata'' * ''Karenia longicanalis'' * ''Karenia mikimotoi'' * ''Karenia papilionacea'' * ''Kare ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karenia Brevis
''Karenia brevis'' is a microscopic, single-celled, photosynthetic organism in the genus '' Karenia''. It is a marine dinoflagellate commonly found in the waters of the Gulf of Mexico. It is the organism responsible for the "Florida red tides" that affect the Gulf coasts of Florida and Texas in the U.S., and nearby coasts of Mexico. ''K. brevis'' has been known to travel great lengths around the Florida peninsula and as far north as the Carolinas. Each cell has two flagella that allow it to move through the water in a spinning motion. ''K. brevis'' is unarmored, and does not contain peridinin. Cells are between 20 and 40 μm in diameter. ''K. brevis'' naturally produces a suite of potent neurotoxins collectively called brevetoxins, which cause gastrointestinal and neurological problems in other organisms and are responsible for large die-offs of marine organisms and seabirds. History ''Karenia brevis'' was named for Dr. Karen A. Steidinger in 2001, and was previously known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harmful Algal Bloom
A harmful algal bloom (HAB) (or excessive algae growth) is an algal bloom that causes negative impacts to other organisms by production of natural algae-produced toxins, mechanical damage to other organisms, or by other means. HABs are sometimes defined as only those algal blooms that produce toxins, and sometimes as any algal bloom that can result in severely lower oxygen levels in natural waters, killing organisms in marine or fresh waters. Blooms can last from a few days to many months. After the bloom dies, the microbes that decompose the dead algae use up more of the oxygen, generating a " dead zone" which can cause fish die-offs. When these zones cover a large area for an extended period of time, neither fish nor plants are able to survive. Harmful algal blooms in marine environments are often called "red tides". It is sometimes unclear what causes specific HABs as their occurrence in some locations appears to be entirely natural, while in others they appear to be a re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brevetoxin
Brevetoxin (PbTx), or brevetoxins, are a suite of cyclic polyether compounds produced naturally by a species of dinoflagellate known as '' Karenia brevis''. Brevetoxins are neurotoxins that bind to voltage-gated sodium channels in nerve cells, leading to disruption of normal neurological processes and causing the illness clinically described as neurotoxic shellfish poisoning (NSP). Although brevetoxins are most well-studied in ''K. brevis'', they are also found in other species of '' Karenia'' and at least one large fish kill has been traced to brevetoxins in ''Chattonella''. Other Brevetoxins: *Brevetoxin-5 (PbTx-5): like PbTx-2, but acetylated hydroxyl group in position 38. *Brevetoxin-6 (PbTx-6): like PbTx-2, but double bond 27-28 is epoxidated. Brevetoxin-B was synthesized in 1995 by K. C. Nicolaou and coworkers in 123 steps with 91% average yield (final yield ~9·10−6) and in 2004 in a total of 90 steps with an average 93% yield for each step (0.14% overall). K. C. Nic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitotic Spindle
In cell biology, the spindle apparatus refers to the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells. It is referred to as the mitotic spindle during mitosis, a process that produces genetically identical daughter cells, or the meiotic spindle during meiosis, a process that produces gametes with half the number of chromosomes of the parent cell. Besides chromosomes, the spindle apparatus is composed of hundreds of proteins. Microtubules comprise the most abundant components of the machinery. Spindle structure Attachment of microtubules to chromosomes is mediated by kinetochores, which actively monitor spindle formation and prevent premature anaphase onset. Microtubule polymerization and depolymerization dynamic drive chromosome congression. Depolymerization of microtubules generates tension at kinetochores; bipolar attachment of sister kinetochores to microtubules emanating from opposite cell pol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Envelope
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 in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitosis
In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintained. Therefore, mitosis is also known as equational division. In general, mitosis is preceded by S phase of interphase (during which DNA replication occurs) and is often followed by telophase and cytokinesis; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. The different stages of mitosis altogether define the mitotic (M) phase of an animal cell cycle—the division of the mother cell into two daughter cells genetically identical to each other. The process of mitosis is divided into stages corresponding to the completion of one set of activities and the start of the next. These stages are preprophase (specific to plant cells), prophase ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-coding DNA
Non-coding DNA (ncDNA) sequences are components of an organism's DNA that do not encode protein sequences. Some non-coding DNA is transcribed into functional non-coding RNA molecules (e.g. transfer RNA, microRNA, piRNA, ribosomal RNA, and regulatory RNAs). Other functional regions of the non-coding DNA fraction include regulatory sequences that control gene expression; scaffold attachment regions; origins of DNA replication; centromeres; and telomeres. Some non-coding regions appear to be mostly nonfunctional such as introns, pseudogenes, intergenic DNA, and fragments of transposons and viruses. Fraction of non-coding genomic DNA In bacteria, the coding regions typically take up 88 % of the genome. The remaining 12 % consists largely of non-coding genes and regulatory sequences, which means that almost all of the bacterial genome has a function. The amount of coding DNA in eukaryrotes is usually a much smaller fraction of the genome because eukaryotic genomes contai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Histone
In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei. They act as spools around which DNA winds to create structural units called nucleosomes. Nucleosomes in turn are wrapped into 30-nanometer fibers that form tightly packed chromatin. Histones prevent DNA from becoming tangled and protect it from DNA damage. In addition, histones play important roles in gene regulation and DNA replication. Without histones, unwound DNA in chromosomes would be very long. For example, each human cell has about 1.8 meters of DNA if completely stretched out; however, when wound about histones, this length is reduced to about 90 micrometers (0.09 mm) of 30 nm diameter chromatin fibers. There are five families of histones which are designated H1/H5 (linker histones), H2, H3, and H4 (core histones). The nucleosome core is formed of two H2A-H2B dimers and a H3-H4 tetramer. The tight wrapping of DNA around histones ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleosome
A nucleosome is the basic structural unit of DNA packaging in eukaryotes. The structure of a nucleosome consists of a segment of DNA wound around eight histone proteins and resembles thread wrapped around a spool. The nucleosome is the fundamental subunit of chromatin. Each nucleosome is composed of a little less than two turns of DNA wrapped around a set of eight proteins called histones, which are known as a histone octamer. Each histone octamer is composed of two copies each of the histone proteins H2A, H2B, H3, and H4. DNA must be compacted into nucleosomes to fit within the cell nucleus. In addition to nucleosome wrapping, eukaryotic chromatin is further compacted by being folded into a series of more complex structures, eventually forming a chromosome. Each human cell contains about 30 million nucleosomes. Nucleosomes are thought to carry epigenetically inherited information in the form of covalent modifications of their core histones. Nucleosome positions in the gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromatin
Chromatin is a complex of DNA and protein found in eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important roles in reinforcing the DNA during cell division, preventing DNA damage, and regulating gene expression and DNA replication. During mitosis and meiosis, chromatin facilitates proper segregation of the chromosomes in anaphase; the characteristic shapes of chromosomes visible during this stage are the result of DNA being coiled into highly condensed chromatin. The primary protein components of chromatin are histones. An octamer of two sets of four histone cores (Histone H2A, Histone H2B, Histone H3, and Histone H4) bind to DNA and function as "anchors" around which the strands are wound.Maeshima, K., Ide, S., & Babokhov, M. (2019). Dynamic chromatin organization without the 30-nm fiber. ''Current opinion in cell biology, 58,'' 95–104. https://doi.o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Fission
Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that takes two arguments * Binary relation, a relation involving two elements * Binary-coded decimal, a method for encoding for decimal digits in binary sequences * Finger binary, a system for counting in binary numbers on the fingers of human hands Computing * Binary code, the digital representation of text and data * Bit, or binary digit, the basic unit of information in computers * Binary file, composed of something other than human-readable text ** Executable, a type of binary file that contains machine code for the computer to execute * Binary tree, a computer tree data structure in which each node has at most two children Astronomy * Binary star, a star system with two stars in it * Binary planet, two planetary bodies of comparable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively, in each homologous chromosome pair, which chromosomes naturally exist as. Somatic cells, tissues, and individual organisms can be described according to the number of sets of chromosomes present (the "ploidy level"): monoploid (1 set), diploid (2 sets), triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets), etc. The generic term polyploid is often used to describe cells with three or more chromosome sets. Virtually all sexually reproducing organisms are made up of somatic cells that are diploid or greater, but ploidy level may vary widely between different organisms, between different tissues within the same organism, and at different stages in an organism's life cycle. Half ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
