lethal:1

adjective
le*thal \ ˈlē-thəl \
circa 1604{ds||1|a|}
  • of, relating to, or causing death
  • capable of causing death
  • gravely damaging or destructive : devastating

lethal:2

noun
lethal \
1917{ds||1||}
  • an abnormality of genetic origin causing the death of the organism possessing it
  • lethal gene

lethal gene

noun
lethal gene \
1939
  • a gene that in some (such as homozygous) conditions may prevent development or cause the death of an organism or its germ cells —called also lethal factor, lethal mutant, lethal mutation
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