Question

Signature-tagged mutagenesis is a genetic method for identifying genes that encode virulence factors. Explain how this method identifies attenuated bacterial strains that are no longer virulent.

Answer 1

Solution:-

Signature tagged mutagenesis is a genetic engineering technique that is used for studying the function of a gene. The technique is based on introducing insertional mutations using transposons in order to study the function of gene in question. Because of insertion of transposon, the structure of protein is affected and the function of protein is lost. Transposons are inserted at random in signature tagged mutagenesis to create the mutants. Each transposon is tagged to a unique sequence tag that is used for transposon identification. If a bacterium after signature tagged mutagenesis exhibits the desired phenotype, it's genome can be sequenced and searched for the tag used in the experiment. Location of the tag in the sequenced genome will give the location of the gene the transposon has disrupted. Once the gene has been identified, the function of gene can be known.

Signature tagged mutagenesis can be used to identify the virulence genes in a bacterium. Random mutations are introduced into a bacterium by signature tagged mutagenesis. The random mutants that are generated are then injected into an animal model such as mouse model. The mutants are then observed for their survival and proliferation in the host. Those mutants that do not survive and proliferate in the host have mutation in the gene required for virulence of the bacterium. This is an example of a negative selection method.

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