We found 6 dictionaries that define the word lethal genes:

General (2 matching dictionaries)

1. lethal genes: Merriam-Webster
2. lethal genes: Wiktionary

Medicine (3 matching dictionaries)

3. lethal genes: Merriam-Webster Medical Dictionary
4. Medical Dictionary (No longer online)
5. online medical dictionary (No longer online)

Science (1 matching dictionary)

6. Agricultural Thesaurus and Glossary (No longer online)

(Note: See lethal_gene as well.)

Definitions from Wiktionary (lethal gene) ▸ noun:  Any gene that brings about the death of an organism carrying it; usually the result of a mutation. ▸ Also see lethal_gene ▸ Words similar to lethal genes ▸ Usage examples for lethal genes ▸ Idioms related to lethal genes ▸ Wikipedia articles (New!) ▸ Words that often appear near lethal genes ▸ Rhymes of lethal genes ▸ Invented words related to lethal genes