Question

what does it mean when the loss-of-function phenotypes are similar between the genes?

Answer 1

Loss of function mutation is also known as null or amorphic mutation. In this an altered gene product lacks the molecular function of the wild type gene. Generally wild type alleles code for a product which is specific for a specific biological function. If there is any type of mutation the function will be lost. Mutation varies the degree of function of that gene. If it is completely lost it is null mutation, and if some function remains but not at par with the wild type allele then is known as leaky mutations.

When a heterozygote cosists of loss of function allele and wild type allele, the level of expression of wild type is sufficient for the production of wild type phenotype. Genetically this would define loss of function gene to be recessive.

If the wild type allele does not compensate for the loss of function allele then in an heterozygote phenotype will be equal to loss of function mutant making that allele dominant. The above statement will mean that loss of function phenotypes are similar due to the mutant allele being dominant.