Balanced lethal genes refer to a genetic phenomenon where the phenotypically normal heterozygotes carrying two different lethal genes are able to survive and reproduce; the homozygotes with both recessive alleles, however, cannot. Essentially, this results in a balanced system where the frequency of the dominant and recessive alleles is maintained without the total loss of the recessive allele. Synonyms for balanced lethal genes include balanced polymorphism, heterozygote advantage, and survival of the fittest. These phrases all refer to the same principle of balancing selective forces while maintaining genetic diversity within a population, though they may have slightly different connotations depending on the specific context in which they are used.