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The nucleoid (meaning nucleus-like) is an irregularly shaped region within the prokaryotic cell that contains all or most of the genetic material. [1] [2] [3] The chromosome of a typical prokaryote is circular, and its length is very large compared to the cell dimensions, so it needs to be compacted in order to fit.
Notch-mediated juxtacrine signal between adjacent cells Notch signaling steps. The Notch signaling pathway is a highly conserved cell signaling system present in most animals. [1] Mammals possess four different notch receptors, referred to as NOTCH1, NOTCH2, NOTCH3, and NOTCH4. [2] The notch receptor is a single-pass transmembrane receptor protein.
Note the irregularly shaped, non-circular cells in the image. Acanthocyte (from the Greek word ἄκανθα acantha, meaning 'thorn'), in biology and medicine, refers to an abnormal form of red blood cell that has a spiked cell membrane, due to thorny projections. [1] [2] A similar term is spur cells.
Biological patterns such as animal markings, the segmentation of animals, and phyllotaxis are formed in different ways. [2]In developmental biology, pattern formation describes the mechanism by which initially equivalent cells in a developing tissue in an embryo assume complex forms and functions. [3]
In 2020, it was announced that Google's AlphaFold, a neural network based on DeepMind artificial intelligence, is capable of predicting a protein's final shape based solely on its amino-acid chain with an accuracy of around 90% on a test sample of proteins used by the team.
Discovered by Fox et al. in 2002, paraspeckles are irregularly shaped compartments in the interchromatin space of the nucleus. [48] First documented in HeLa cells, where there are generally 10–30 per nucleus, [ 49 ] paraspeckles are now known to also exist in all human primary cells, transformed cell lines, and tissue sections. [ 50 ]
The green box (central) may represent an evolutionary grade (paraphyletic), a group united by conservative anatomical and physiological traits rather than phylogeny. The flanking red and blue boxes are clades (i.e., complete monophyletic subtrees). A grade is a taxon united by a level of morphological or physiological complexity.
An operational taxonomic unit (OTU) is an operational definition used to classify groups of closely related individuals. The term was originally introduced in 1963 by Robert R. Sokal and Peter H. A. Sneath in the context of numerical taxonomy , where an "operational taxonomic unit" is simply the group of organisms currently being studied. [ 1 ]