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Lethal genes

A lethal gene is one whose presence in the genotype blocks or hinders the normal development of the individual, causing death before reaching sexual maturity.

If the gene does not cause death, but has negative effects on the individual, reducing their ability to survive or reproduce, it is called a deleterious gene.

There are different types of lethal genes:

  • According to the deaths they produce:
    • Complete: Produces death in 90% of cases or more.
    • Semi-lethal: More than 50% of the carriers die.
    • Sublethal: Produces death to less than 10% of carriers.
  • By the development phase in which they act:
    • Gametics: They cause the non-functionality of gametes.
    • Zygotic, embryonic or post-embryonic: Incompatible with the survival of the zygote.
  • By the genes in which they are located:
    • Linked to sex.
    • Autosomal lethal genes.
  • Depending on whether they are dominant or recessive:
    • Dominant lethal: They have a lethal effect in both homozygosity and heterozygosity.
    • Recessive lethal: Its lethal effect only in homozygosity.


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