Lethal Genes

LETHAL GENES, genes (see), causing a fatal outcome in the homozygous state. Along with them, a large number of semi-lethal factors are known, which very often lead to the birth of various kinds of non-viable monsters or simply in some way affect the viability of organisms. At the present time, L. g. are known in Drosophila, mice, rabbits, dogs, pigs, sheep, horses, cattle, birds, a number of plants, in humans, etc. An example of a semi-lethal factor in humans can be hemophilia, in the presence of which instead of normal blood clotting in 5-5^th/₂ min. this process sometimes drags on for 120 min. and even more; the lethal gene of hemophilia is localized in the sex chromosome, which explains the transmission of this trait to half of the sons from an outwardly healthy mother who is heterozygous for this factor. - Lethal and sublethal mutations characterize domesticated forms of animals, since in the wild state the energetic struggle for existence destroys all organisms possessing mutations that cause one or another degenerative signs.