Final answer:
An organism with a null allele for an essential gene may not be able to perform the necessary function of the gene, leading to developmental issues or death depending on the specifics of the gene and its requirements. This is referred to as a recessive lethal inheritance pattern.
Step-by-step explanation:
An organism that has a null allele for an essential gene will experience various outcomes depending on the specific gene and life stage requirements. The null allele is nonfunctional and cannot perform the necessary function of the essential gene.
In cases where the essential gene is required for normal development, individuals with a homozygous recessive genotype for the nonfunctional allele may fail to develop past fertilization, die in utero, or die later in life.
This type of inheritance pattern, where the allele is only lethal in the homozygous form, is referred to as recessive lethal.