Final answer:
A dominant mutant allele that changes a gene such that it yields a new or abnormal function is called gain-of-function mutation. A dominant mutant allele that results in a new or abnormal function is called a gain-of-function mutation, which can be dominant negative if it adversely affects the wild-type gene product.
Step-by-step explanation:
A dominant mutant allele that changes a gene such that it yields a new or abnormal function is called gain-of-function mutation. This type of mutation results in a gene product that enhances the function of the wild-type gene product or changes its distribution in the body. For example, the Antennapedia mutation in Drosophila expands the distribution of the gene product and results in the development of legs on the head instead of antennae.
A dominant mutant allele that results in a new or abnormal function is called a gain-of-function mutation, which can be dominant negative if it adversely affects the wild-type gene product.
A dominant mutant allele that changes a gene in a way that it provides a new or abnormal function is often referred to as a gain-of-function mutation. These types of alleles can cause a phenotype to be expressed even when only one copy is present in the genotype (heterozygous state), and they sometimes result in a constitutively activated protein that overpowers the "normal" gene product. An example of this is seen with the Antennapedia mutation in Drosophila, where the mutant allele alters gene product distribution, leading to the development of legs in place of antennae on the head.
Dominant mutations can also be categorized as dominant negative or antimorphic mutations when the mutant gene product adversely affects the normal, wild-type gene product. In such scenarios, the mutant protein might block or alter the function of the normal protein. Notably, gain-of-function mutations often play a role in the development of various cancers as they can turn proto-oncogenes into oncogenes.