Final answer:
The most common scenario is that loss of function mutations are recessive because a single functional gene copy, which indicates haplosufficiency, is typically enough to keep normal function.
Step-by-step explanation:
Most loss of function mutations are recessive because most genes are haplosufficient
Explanation: Loss of function mutations often result in a gene product that is less active or inactive compared to the wild-type gene. In many cases, a single functional copy of a gene is enough to maintain normal function, this is known as haplosufficiency. Therefore, an individual with one wild-type allele and one nonfunctional allele (heterozygote) usually has sufficient gene activity to be phenotypically normal.
As a result, the wild-type allele is dominant over the defective one, and the loss of function mutation displays a recessive inheritance pattern. Dominant negative mutations are different and refer to gain-of-function mutations where the mutated gene product interferes with the normal function. However, in the case of haplosufficiency, the presence of a wild-type allele allows for normal functioning, hence the mutation appears recessive.