semi-lethaladj.n.

1917 Proc. National Acad. Sci. U.S.A. 3 621 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.

1927 Brit. Jrnl. Exper. Biol. 5 124 This mutation appears to be semi-lethal, as the animals homozygous for it are delicate and difficult to rear.

1937 Genetics 22 471 A group of nine changes obtained from male 8..proved to be semilethal.

1962 I. H. Herskowitz Genetics xxviii. 239 Autosomes II, III, and IV of wild-type flies were individually made homozygous to detect the presence of recessive mutants..that are lethal (causing death of all individuals before adulthood), or semilethal (causing more than 90 and less than 100 per cent mortality before adulthood), or subvital (causing significantly less than normal but greater than 10 per cent survival to adulthood)... About 25% of all autosomes tested this way carried a recessive lethal or semilethal mutant.

1973 K. Mather Genetical Struct. Populations ii. 21 Not all genes that affect viability are, however, completely lethal. Of some 3000 chromosomes tested in Drosophila willistoni..over 35% carried genes that were lethal or semi-lethal. About half of the remainder carried other genes affecting the viability of flies homozygous for them.

1919 Proc. Soc. Exper. Biol. & Med. 1919–20 17 12 Four of the lethals (perhaps five) are more strictly speaking ‘semi~lethals’, as they occasionally allow the male possessing them to live.

1944 Proc. National Acad. Sci. U.S.A. 30 174 Fu is a tail mutation closely resembling Ki. It acts as a semi~lethal, some Fu Fu being viable.

1974 Nature 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.