1. SYN: reproduction (1). 2. A discrete stage in succession of descent; e.g., father, son, and grandson are three generations. [L. generatio, fr. genero, pp. -atus, to beget]
- asexual g. reproduction by fission, gemmation, or in any other way without union of the male and female cell, or conjugation. SEE ALSO: parthenogenesis. SYN: heterogenesis (2), nonsexual g..
- filial g. (F) the offspring of a genetically specified mating : first filial g. (symbol F1), the offspring of parents of contrasting genotypes; second filial g. (F2), the offspring of two F1 individuals; third filial g. (F3), fourth filial g. (F4), etc., the offspring in succeeding generations of continued inbreeding of F1 descendents.
- nonsexual g. SYN: asexual g..
- parental g. (P1) the parents of a mating, commonly experimental, involving contrasting genotypes; the original mating of a genetic experiment; parents of the F1 g..
- sexual g. reproduction by conjugation, or the union of male and female cells, as opposed to asexual g..
- skipped g. a phenomenon of pedigrees in which a gene is transmitted from one affected person to another through a phenotypically unaffected person, as by recessivity (especially for X-linked traits), epistasis, variable expressivity, or absence of an environmental challenge such as a toxin. Except at a crass phenotypic level ( e.g., clinical or commercial) this term becomes progressively less useful as the mechanisms are elucidated.
- spontaneous g. the false concept according to which living matter can arise by the vitalization of nonliving matter. SEE ALSO: biogenesis. SYN: heterogenesis (3).

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gen·er·a·tion .jen-ə-'rā-shən n
1 a) a body of living beings constituting a single step in the line of descent from an ancestor
b) a group of individuals born and living contemporaneously
2) the average span of time between the birth of parents and that of their offspring
3) the action or process of producing offspring: PROCREATION
gen·er·a·tion·al -shnəl, -shən-əl adj

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gen·er·a·tion (jen″ər-aґshən) [L. generatio] 1. reproduction (def. 1). 2. a class composed of all individuals removed by the same number of successive ancestors from a common predecessor, or occupying positions on the same level in a pedigree chart. 3. in pharmacology, a subgroup of a larger class of agents that share a certain characteristic and usually were developed around the same time as each other.

Medical dictionary. 2011.