A mutant is an organism, cell or gene that carries a mutation resulting in a DNA sequence different from the standard or wild‑type.
Explanation
When the genetic material of an organism changes and the alteration becomes fixed, the resulting variant is described as a mutant. Mutations can be spontaneous or induced by mutagens, and they range from single nucleotide substitutions to large chromosomal rearrangements. In multicellular organisms, mutants may arise during development and be present only in certain tissues, or they may occur in germ cells and be inherited by offspring. The term wild‑type refers to the most common form of a gene or phenotype in a population; mutants are variants that differ from this reference. Mutations can lead to loss‑of‑function, gain‑of‑function or altered regulation of a gene. In research, mutants are invaluable tools for dissecting gene function, genetic pathways and phenotypic outcomes. Forward genetics screens identify mutants with particular traits and then map the underlying mutations, while reverse genetics deliberately introduces mutations to study their effects. Advances in gene editing, such as CRISPR–Cas systems, allow targeted creation of mutants in virtually any organism.
Examples and Applications
Classic examples include Drosophila melanogaster mutants with white eyes, curled wings or altered body colour that helped elucidate principles of inheritance. In bacteria, auxotrophic mutants lacking the ability to synthesise specific metabolites have been used to map metabolic pathways and study gene regulation. Knockout mice lacking specific genes are generated to model human diseases such as cystic fibrosis or muscular dystrophy. Mutant strains of viruses are attenuated for use in vaccines. In medicine, somatic mutants can give rise to cancers when mutations activate oncogenes or disable tumour suppressor genes. Conversely, artificially generated mutants of crops may exhibit improved traits such as resistance to herbicides or pests. Mutants are also central to screening programs that identify genes involved in development, behaviour and disease.
Recognising and studying mutants provides insight into the relationship between genotype and phenotype, advancing our understanding of biology and enabling the development of new therapies and technologies.
Related Terms: Mutation, Wild-type, Allele, Gene knockout, Phenotype