Glossary Sheet Flashcards
Fate
The range of tissues or cell types normally generated by a given cell of tissue in the embryo. Compare with the concept of developmental potential, which is the range of tissues or cell types that a given cell is capable of generating.
Fate map
A spatial map of the fates of different regions of an embryo at a particular stage of development. Usually applied to a group of cells. There term cell lineage is more often used to refer to the collection of fates generated by a single cell
Cell lineage
The collection of a descendants of a single cell during normal development. The term is more usually reserved for the experimental situation of following, or mapping these descendants and their ultimate fates by direct observation or by some marking method that allows the progeny of the parent cell to be identified. The expression cell analysis does not formally differ from fate mapping, but in practise is used for mapping the progeny of single cells while the later implies that the progeny of a group cells is studied
Specification
The tendency of a cell or a group of cells, when cultured in isolation from the rest of the embryo, and under ‘neutral conditions, to differentiate into a particular direction. Unfortunately, it is experimentally feasible to determine this only a few species (like xenopus and zebrafish) where ‘neutral’ conditions, in a simple saline solution, are possible. Even in these species, it might be argued that a simple saline solution is not neutral.
Commitment
Most authors use the term commitment and determination interchangeably, to mean an irreversible decision to differentiate in a particular direction.
Determination
An irreversible decision made by an undifferentiated cell which restricts its differentiation into a smaller subset of cell types. A cell becomes determined when its developmental potential no longer differs from its fate.
Developmental potential
The range of all the possible phenotypes that can be produced by the descendants of a cell or group of cells. This concept differs from fate: the fate of a cell or group of cells is the range of phenotypes produced by those cells in normal development, while their developmental potential includes all the possible phenotypes to which the cell can give rise.
Differentiation
The expression of manifestation of the fate of a cell. A differentiated cell expressed characteristic proteins and has a clearly defined morphology which identify it as a member of a defined histological type. The process of differentiation is probably always irreversible.
Induction
An interaction between one (inducing) tissue and another (responding) tissue as a result of which the responding tissue undergoes a change in its direction of differentiation. Slack has suggested the general rule that by comparing a fate map with a specification map of the same stage of development, the differences between the two maps reveal he sites and times where induction takes place.
Competence
The ability of a cell or tissue to respond to a particular inducing signal. Competence is believed to depend largely on the expression of appropriate receptors specific for the inducing molecule(s) by the responding cells, and of an intact signal transduction cascade that can result in specific gene activation in response to a signal.
Morphogenetic field
A portion of an embryo contained within well-defined boundaries, which can develop independently, without instructive influences from the rest of the embryo. An important property of morphogenetic fields is that they are capable of regulation, that is, any portion of the field can reconstitute the whole field. As development proceeds, fields subdivide, coming smaller and more numerous.
Regulation and Regeneration
Is the ability of a portion of a morphogenetic field to reconstitute the entire field. Regeneration is a more restricted version of regulation, which relates to the ability of a morphogenetic field to compensate for missing parts. At early stages of development, when the entire embryo is a single field, regulation defines the ability of parts of some embryos to reconstitute the entire embryo. In two cell-stage amphibians, or example, separation of the two blastomeres can allow each blastomere to produce a whole embryo.
