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98:] long crest feathers evolve by gradual modification of ancestral head feathers? Or are they descendants of wing feathers, developmentally transplanted onto the head". This idea sets the tone for the rest of her book which goes into depth about developmental novelties and their relation to evolution. Heterotopy is a somewhat obscure but well demonstrated example of how developmental change can lead to novel forms. The central concept is that a feature seen in one area of an organism has had its location changed in evolutionary lineages.
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Molecular analysis shows that proteins that seem to have a single specific function are instead found in many different tissue types. One example of this phenomenon is crystallin, a clear protein that makes up the lens of the eye; it is also has structural functions in the heart.
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Wagner et al., suggest that chitin might have a microscopic function observed in cell to cell signaling and the manufacture of insect cuticle for example might represent a recurrent change in the location of expression
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Heterotopy in molecular biology is the name given to the expression or placement of a gene product from what is typically found in one area to another area. It can also be further expanded to a subtle form of
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It is thought that because so many organisms share such a profound degree of genetic and molecular similarity that shifts in the location of expression might be a regular occurrence throughout time.
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distributions of traits. But actual phylogenetic analysis supports a monophyletic model as does evolutionary theory. Heterotopy is used to explain this and there are so commonly cited examples.
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is the presence of a particular tissue type at a non-physiological site, but usually co-existing with original tissue in its correct anatomical location. In other words, it implies
69:. Heterotopia within the brain is often divided into three groups: subependymal heterotopia, focal cortical heterotopia and band heterotopia. Another example is a
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where a gene product used for one underlying purpose in a diverse group of organisms can re-emerge repeatedly to produce seemingly
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Speculative, but however Chitin synthase is maintained in many lineages where it does not have an obvious macroscopic function.
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a very durable structural protein used in surgical sutures as well as durable
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refers to an altered location of trait expression. In her book
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tissue, in addition to retention of the original tissue type.
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Presence of some localized tissue type elsewhere in the body
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showing a duodenal biopsy with gastric heterotopia;
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92:and comments on the back cover "Did it's [
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126:but is common to many animals especially
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86:Developmental Plasticity and Evolution
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53:In neuropathology, for example,
102:Heterotopy in molecular biology
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90:sulphur crested cockatoo
55:gray matter heterotopia
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71:Meckel's diverticulum
63:cerebral white matter
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237:Congenital disorders
220:Wray and McClay 1989
211:Wagner et al., 1993
190:West-Eberhard, 2003
136:African clawed frog
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128:crustaceans
61:within the
59:gray matter
39:heterotopia
178:References
172:Heterotopy
167:Choristoma
109:exaptation
82:heterotopy
67:ventricles
24:Micrograph
124:varnishes
231:Category
161:See also
49:Examples
35:medicine
201:Biology
132:insects
78:biology
43:ectopic
148:chitin
120:chitin
130:and
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95:sic
76:In
65:or
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