Final answer:
In the case of an organism that is a heterozygote for an essential gene, there is a chance that some offspring may be homozygous recessive for the nonfunctional allele, which could result in the failure to develop or death at various life stages.
Step-by-step explanation:
In the case of an organism that is a heterozygote for an essential gene, the wild-type allele, which functions at a capacity sufficient to sustain life, is considered dominant over the nonfunctional allele. However, if two heterozygous parents mate, there is a chance that in one quarter of their offspring, individuals may be homozygous recessive for the nonfunctional allele. Because the gene is essential, these individuals might fail to develop past fertilization, die in utero, or die later in life, depending on what life stage requires this gene. This inheritance pattern is referred to as recessive lethal.