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Macrocyst
A macrocyst is an aggregate of cells of Dictyostelids formed during sexual reproduction enclosed in a cellulose wall. If two amoebae of different mating types are present in a dark and wet environment, they can fuse during aggregation to form a giant cell. The giant cell will then engulf the other cells in the aggregate and encase the whole aggregate in a thick, cellulose wall to protect it. This is known as a macrocyst. Inside the macrocyst, the giant cell divides first through meiosis, then through mitosis to produce many haploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Here ''sets of chromosomes'' refers to the num ... amoebae that will be released to feed as normal amoebae would. See also * Life cycle and reproduction of Dictyostelium discoideum References Mycetozoa {{amoebozoa-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Dictyostelium Discoideum
''Dictyostelium discoideum'' is a species of soil-dwelling Amoeboid, amoeba belonging to the phylum Amoebozoa, infraphylum Mycetozoa. Commonly referred to as slime mold, ''D. discoideum'' is a eukaryote that transitions from a collection of unicellular amoebae into a multicellular slug and then into a fruiting body within its lifetime. Its unique asexual Biological life cycle, life cycle consists of four stages: vegetative, aggregation, migration, and culmination. The life cycle of ''D. discoideum'' is relatively short, which allows for timely viewing of all stages. The cells involved in the life cycle undergo movement, chemical signaling, and development, which are applicable to human cancer research. The simplicity of its life cycle makes ''D. discoideum'' a valuable model organism to study genetic, cellular, and biochemical processes in other organisms. Natural habitat and diet In the wild, ''D. discoideum'' can be found in soil and moist leaf litter. Its primary diet consists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Dictyostelid
The dictyostelids (Dictyostelia/Dictyostelea, ICZN, Dictyosteliomycetes, ICBN) or cellular slime molds are a group of slime molds or social amoebae. Multicellular behavior When food (normally bacteria) is readily available dictyostelids behave as individual amoebae, which feed and divide normally. However, when the food supply is exhausted, they aggregate to form a multicellular assembly, called a pseudoplasmodium, grex, or slug (not to be confused with the gastropod mollusc called a slug). The grex has a definite anterior and posterior, responds to light and temperature gradients, and has the ability to migrate. Under the correct circumstances the grex matures forming a sorocarp (fruiting body) with a stalk supporting one or more sori (balls of spores). These spores are inactive cells protected by resistant cell walls, and become new amoebae once food is available. In ''Acytostelium'', the sorocarp is supported by a stalk composed of cellulose, but in other dictyostelids ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Sexual Reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes ( diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes. In placental mammals, sperm cells exit the penis through the male urethra and enter the vagina during copulation, while egg cells enter the uterus through the oviduct. Other vertebrates of both sexes possess a cloaca for the release of sperm or egg cells. Sexual reproduction is the most common life cycle in multicellular eukaryotes, such as animals, fungi and plants. Sexual reproduction also occurs in some unicellular eukaryotes. Sexual reproduction does not occur in pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Cell Wall
A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, and functions as a selective barrier. Another vital role of the cell wall is to help the cell withstand osmotic pressure and mechanical stress. While absent in many eukaryotes, including animals, cell walls are prevalent in other organisms such as fungi, algae and plants, and are commonly found in most Prokaryote, prokaryotes, with the exception of Mollicutes, mollicute bacteria. The composition of cell walls varies across taxonomic groups, species, cell type, and the cell cycle. In Embryophyte, land plants, the primary cell wall comprises Polysaccharide, polysaccharides like cellulose, hemicelluloses, and pectin. Often, other Polymer, polymers such as lignin, suberin or cutin are anchored to or embedded in plant cell walls. Algae exhibit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Amoeba
An amoeba (; less commonly spelled ameba or amœba; : amoebas (less commonly, amebas) or amoebae (amebae) ), often called an amoeboid, is a type of Cell (biology), cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopodia, pseudopods. Amoebae do not form a single Taxonomy (biology), taxonomic group; instead, they are found in every major Lineage (evolution), lineage of eukaryote, eukaryotic organisms. Amoeboid cells occur not only among the protozoa, but also in fungi, algae, and animals. Microbiologists often use the terms "amoeboid" and "amoeba" interchangeably for any organism that exhibits amoeboid movement. In older classification systems, most amoebae were placed in the Class (biology), class or subphylum Sarcodina, a grouping of Unicellular organism, single-celled organisms that possess pseudopods or move by protoplasmic flow. However, molecular phylogenetic studies have shown that Sarcodina is not a monophyletic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Mating Type
Mating types are the microorganism equivalent to sexes in multicellular lifeforms and are thought to be the ancestor to distinct sexes. They also occur in multicellular organisms such as fungi. Definition Mating types are the microorganism equivalent to sex in higher organisms and occur in isogamous species. Depending on the group, different mating types are often referred to by numbers, letters, or simply "+" and "−" instead of "male" and "female", which refer to " sexes" or differences in size between gametes. Syngamy can only take place between gametes carrying different mating types. Mating types are extensively studied in fungi. Among fungi, mating type is determined by chromosomal regions called mating-type loci. Furthermore, it is not as simple as "two different mating types can mate", but rather, a matter of combinatorics. As a simple example, most '' basidiomycete'' have a "tetrapolar heterothallism" mating system: there are two loci, and mating between two individua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Giant Cell
A giant cell (also known as a multinucleated giant cell, or multinucleate giant cell) is a mass formed by the union of several distinct cells (usually histiocytes), often forming a granuloma. Although there is typically a focus on the pathological aspects of multinucleate giant cells (MGCs), they also play many important physiological roles. Osteoclasts are a type of MGC that are critical for the maintenance, repair, and remodeling of bone and are present normally in a healthy human body. Osteoclasts are frequently classified and discussed separately from other MGCs which are more closely linked with disease. Non-osteoclast MGCs can arise in response to an infection, such as tuberculosis, herpes, or HIV, or as part of a foreign body reaction. These MGCs are cells of monocyte or macrophage lineage fused together. Similar to their monocyte precursors, they can phagocytose foreign materials. However, their large size and extensive membrane ruffling make them better equipped t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Meiosis
Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy of each chromosome (haploid). Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and a female will fuse to create a zygote, a cell with two copies of each chromosome. Errors in meiosis resulting in aneuploidy (an abnormal number of chromosomes) are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number of chromosomes as the original parent cell. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Mitosis
Mitosis () is a part of the cell cycle in eukaryote, eukaryotic cells in which replicated chromosomes are separated into two new Cell nucleus, nuclei. Cell division by mitosis is an equational division which gives rise to genetically identical cells in which the total number of chromosomes is maintained. Mitosis is preceded by the S phase of interphase (during which DNA replication occurs) and is followed by telophase and cytokinesis, which divide the cytoplasm, organelles, and cell membrane of one cell into two new cell (biology), cells containing roughly equal shares of these cellular components. The different stages of mitosis altogether define the mitotic phase (M phase) of a cell cycle—the cell division, 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 ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Haploid
Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, respectively, in each homologous chromosome pair—the form in which chromosomes naturally exist. Somatic cells, Tissue (biology), tissues, and Individual#Biology, 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 polyploidy, polyploid is often used to describe cells with three or more sets of chromosomes. Virtually all sexual reproduction, sexually reproducing organisms are made up of somatic cells that are diploid or greater, but ploidy level may vary wid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
