What are lethal alleles?

Lethal alleles are specific types of mutated genes that can lead to the death of an organism when they are expressed in a certain genotype. This typically occurs when an individual inherits two copies of a lethal allele, resulting in a genotype that affects critical biological functions, ultimately leading to mortality.

For example, in some genetic diseases, if an organism has two copies of a recessive lethal allele, the combination prevents the organism from developing normally, resulting in early death before it can reproduce. This highlights the importance of understanding how certain alleles can have a profound impact on survival and reproductive success. In contrast, the other options describe different genetic scenarios that do not align with the definition of lethal alleles.