homology


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homology

(hōmŏl`əjē), in biology, the correspondence between structures of different species that is attributable to their evolutionary descent from a common ancestor. For example, the forelimbs of vertebrates, such as the wing of bird or bat, and the foreleg of an amphibian, are homologous; there is an almost identical number of bones in the limbs, and the pattern construction is identical. Homologous structures do not necessarily have to have the same function; the wings of birds and forelegs of a horse are homologous through they clearly serve different functions. Analogyanalogy,
in biology, the similarities in function, but differences in evolutionary origin, of body structures in different organisms. For example, the wing of a bird is analogous to the wing of an insect, since both are used for flight.
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 is the functional similarity between structures that do not have a common origin; for example, the wings of birds and those of insects are analogous.

Homology

 

in biology, a similarity of organs constructed in the same way and developing from identical embryonic rudiments in different animals and plants; such homologous organs may be dissimilar in appearance and perform different functions.

The determination of homology and its juxtaposition to analogy were proposed by the English scientist R. Owen (1843), who distinguished specific homology from serial homology. He defined specific homology as the correspondence of an organ in one animal to an organ in another, in terms of position and relationship with other parts of the body (for example, the human arm, the cetacean flipper, and the avian wing). Serial homology, or homodynamy, he understood to be correspondence in the same animal of body parts located along the same longitudinal axis (for example, the human arm and leg). The commonality of origin of organisms was first given as the natural-historical explanation for homology by C. Darwin (1859). The German anatomist C. Gegenbaur (1898) distinguished complete and incomplete homology. In complete homology the similarity of organs according to their position and connections with other organs is not disrupted by variations in form and size; in incomplete homology certain parts of organs may disappear through evolution (defective homology), or new parts may appear (augmentative homology). The combination of loss of some parts of the body and the new formation of others is called imitative homology (German biologist M. Fürbringer).

The morphological criteria for homology are similar position and structure of the organs and the presence of transitional forms. The ontogenetic criterion of homology is the development of organs from similar embryonic rudiments. An example of homology in plants is that of leaves that have been modified due to the results of various functions and converted into flower petals, stamens, or one of several kinds of thorns. Specific instances of homology are homodynamy, homonomy, and homotypy.

REFERENCES

Shmal’gauzen, I. I. Osnovy sravnitel’noi anatomii pozvonochnykh zhivotnykh, 2nd ed. Moscow, 1935.
Darwin, C. Proiskhozhdenie vidov putem estestvennogo otbora: Soch., vol. 3. Moscow-Leningrad, 1939.
Bliakher, L. la. “Analogiia i gomologiia.” In the collection Ideia razvitiia v biologii. Moscow, 1965.
Haeckel, E. Generelle Morphologie der Organismen, vols. 1–2. Berlin, 1866.
Gegenbaur, C. Vergleichende Anatomie der Wirbelthiere. Leipzig, 1898.
Owen, R. On the Archetype and Homologies of the Vertebrate Skeleton. London, 1847.

L. IA. BLIAKHER


Homology

 

(in mathematics). (1) In projective geometry, a one-to-one transformation of a projective plane onto itself, in which the linear distribution of points is preserved and all points of a given straight line—the axis of homology—remain fixed.

(2) A concept of topology. In the simplest case homology refers to the property by which a closed curve on a given surface is the boundary of a certain part of the surface. For example, the curve l on the surface of a torus is the boundary of a part 5 of this surface; it is said to be homologous to zero. The curve λ is not homologous to zero since it is not a boundary of any part of the surface; a cut along it will not result in a piece of the torus falling out (see Figure 1).

Figure 1

homology

[hə′mäl·ə·jē]
(biology)
A fundamental similarity between structures or processes in different organisms that usually results from their having descended from a common ancestor.
(chemistry)
The relation among elements of the same group, or family, in the periodic table.
(organic chemistry)
That state, in a series of organic compounds that differ from each other by a CH2 such as the methane series Cn H2 n +2, in which there is a similarity between the compounds in the series and a graded change of their properties.

homology

1. Chem the similarities in chemical behaviour shown by members of a homologous series
2. Zoology the measurable likenesses between animals, as used in grouping them according to the theory of cladistics
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These common submatrices are used as models in some remote homology detection methods (6-7).
Partial sequence and homology search of Dacryopinax spathularia ITS region (447bp)
A knot concordance invariant c having certain properties, like signature [sigma], Rasmussen's invariant s [Ra], the [tau] invariant of knot Floer homology [OS1], gives rise to a quasi-morphism [[rho].
In structural genomics and proteomics, homology modeling is one of the reliable method for comparative analysis.
Phylogenetic analysis of PVX Pakistani isolate was done for determining the homology and differences with other reported sequences on NCBI as done by Tian et al.
The second section provides the general notions of digital images with [kappa]-adjacency relations, digital homotopy and homology groups.
Though the two-phase algorithm was shown to have efficiency gain of up to two orders of magnitude compared to the original Smith-Waterman algorithm alone [29], it is still not efficient enough to be applied alone for off-target homology search for a large number of siRNA sequences, such as the whole-genome siRNA design and off-target detection.
In the case of drug design protocols, the availability of membrane protein structures or, as we saw before, the possibility of gaining structural information by homology modeling combined with experiments, will allow a shift paradigm from ligand-based to target-based drug design.
a) Enumerative criterion: We give a simple criterion for the r-stackedness in terms of h-vectors and Betti numbers for homology manifolds with boundary (Theorem 3.
In view of these results one may ask that if (X, Y) is a q-Runge pair of q-complete spaces of dimension n the homology group [H.
A protein according to the present invention are concerned with (a), (b) or (c), namely (a) a protein comprising an amino acid sequence selected from the group consisting of the amino acid sequences shown in SEQ ID NOs: 2, 4, and 6; (b) a protein that has at least 50% homology to the protein comprising the amino acid sequence of the sequence described in (a) and having saponin-decomposing activity; or (c) a protein comprising a modified amino acid sequence of the sequence described in (a) that has one or more amino acid residues deleted, substituted, inserted, or added and having saponin-decomposing activity.
falciparum for the 545 nuclear-encoded apicoplast targeted genes and looked for their genetic homology with P vivax.