Signature tagged mutagenesis
Encyclopedia
Signature-tagged mutagenesis (STM) is a genetic
technique used to study gene function. Recent advances in genome sequencing have allowed us to catalogue a large variety of organisms genomes, but the function of the genes they contain is still largely unknown. Using STM, a scientist may infer what function the product of a particular gene has by disabling it and observing the effect on the organism. The original and most common use of STM is to discover which genes in a pathogen
are involved in virulence in its host, so that better medical treatments can be designed.
; a transposon
is used which inserts itself into the gene sequence. When that gene is transcribed and translated into a protein, the insertion of the transposon affects the protein structure and (in theory) prevents it from functioning. In STM, mutants are created by random transposon insertion and each transposon contains a different 'tag' sequence that uniquely identifies it. If an insertional mutant bacterium exhibits a phenotype of interest, such as susceptibility to an antibiotic
it was previously resistant to, then the scientist will sequence its genome and run a search (on a computer) for any of the tags used in the experiment. When a tag is located, the gene that it disrupts is also thus located (It will reside somewhere between a start and stop codon which mark the boundaries of the gene).
Scientists may use STM to discover which genes are critical to a pathogen's virulence by injecting a 'pool' of different random mutants into an animal model such as a mouse and observing which of the mutants survive and proliferate in the host. Those mutant pathogens that didn't survive in the host must have had an inactivated gene that was needed for virulence. This is hence an example of a negative selection method.
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
technique used to study gene function. Recent advances in genome sequencing have allowed us to catalogue a large variety of organisms genomes, but the function of the genes they contain is still largely unknown. Using STM, a scientist may infer what function the product of a particular gene has by disabling it and observing the effect on the organism. The original and most common use of STM is to discover which genes in a pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
are involved in virulence in its host, so that better medical treatments can be designed.
Basic Premise
The gene in question is inactivated by insertional mutationMutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
; a transposon
Transposon
Transposable elements are sequences of DNA that can move or transpose themselves to new positions within the genome of a single cell. The mechanism of transposition can be either "copy and paste" or "cut and paste". Transposition can create phenotypically significant mutations and alter the cell's...
is used which inserts itself into the gene sequence. When that gene is transcribed and translated into a protein, the insertion of the transposon affects the protein structure and (in theory) prevents it from functioning. In STM, mutants are created by random transposon insertion and each transposon contains a different 'tag' sequence that uniquely identifies it. If an insertional mutant bacterium exhibits a phenotype of interest, such as susceptibility to an antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
it was previously resistant to, then the scientist will sequence its genome and run a search (on a computer) for any of the tags used in the experiment. When a tag is located, the gene that it disrupts is also thus located (It will reside somewhere between a start and stop codon which mark the boundaries of the gene).
Scientists may use STM to discover which genes are critical to a pathogen's virulence by injecting a 'pool' of different random mutants into an animal model such as a mouse and observing which of the mutants survive and proliferate in the host. Those mutant pathogens that didn't survive in the host must have had an inactivated gene that was needed for virulence. This is hence an example of a negative selection method.