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semi-ˈlethal, a. and n. Genetics.
[semi- 8 a.]
A. adj. Of an allele or a chromosomal abnormality: causing impaired viability of most of the individuals homozygous for it.
1917Proc. Nat. Acad. Sci. III. 621 The viability of the three sex-linked dominants was..already known; the remaining six dominants were tested. In all, it was found that three of the nine are not lethal, one..is semi-lethal, and five..are completely lethal when homozygous. 1927Brit. Jrnl. Exper. Biol. V. 124 This mutation appears to be semi-lethal, as the animals homozygous for it are delicate and difficult to rear. 1937Genetics XXII. 471 A group of nine changes obtained from male 8..proved to be semilethal. 1962,1973[see lethal a. 1 d].
B. n. A semi-lethal gene.
1919Proc. Soc. Exper. Biol. & Med. XVII. 12 Four of the lethals (perhaps five) are more strictly speaking ‘semi⁓lethals’, as they occasionally allow the male possessing them to live. 1944Proc. Nat. Acad. Sci. XXX. 174 Fu is a tail mutation closely resembling Ki. It acts as a semi⁓lethal, some Fu Fu being viable. 1974Nature 2 Aug. 451/3 Most of such populations in North America and Europe proved to be polymorphic for variant genes, usually embryonic lethals or semilethals, belonging to the T series. |