Prof Dr C V Chittibabu
HOD of Botany (Rtd on April 30th 2024)
Presidency College (University of Madras),
Chennai 600 005, Tamil Nadu, India Travel Series 13
Microbial Genetics: Fundamentals
(10 Capsules)
(10 Capsules)
1. Transformation: The process by which bacterial cells take up free DNA molecules from their surroundings. Example: Natural Transformation: Streptococcus pneumoniae can take up free DNA from its surroundings, allowing it to acquire new traits such as antibiotic resistance. Artificial Transformation: Escherichia coli (E. coli) can be transformed with a plasmid containing a gene for antibiotic resistance.
2. Transduction: The transfer of genetic material from one bacterium to another through a viral vector (bacteriophage). Example: Salmonella enterica can be transduced with a bacteriophage carrying a gene for antibiotic resistance, allowing the bacterium to acquire that trait.
3. Conjugation: A process of direct cell-to-cell transfer of genetic material, typically plasmids, between bacterial cells. Example: E. coli can conjugate with another E. coli cell, transferring a plasmid carrying a gene for antibiotic resistance. This process is mediated by a conjugation pilus.
4. Plasmid: A small, self-replicating circular DNA molecule found in bacterial cells, often carrying genes that confer advantageous traits. Example: The pBR322 plasmid is a commonly used plasmid in genetic engineering that carries genes for antibiotic resistance and can be easily manipulated in the laboratory.
5. Genetic Recombination: The process by which genetic material is exchanged and recombined between different DNA molecules, resulting in new combinations of genes. Example: Homologous Recombination: When a bacteriophage infects a bacterium, it can integrate its genetic material into the host’s genome through homologous recombination.
6. Mutation: A change in the DNA sequence of an organism, which can result in changes to the organism’s phenotype. Example: A point mutation in the rpoB gene of Mycobacterium tuberculosis can confer resistance to the antibiotic rifampicin.
7. Gene Expression: The process by which the information encoded in a gene’s DNA is converted into a functional product, such as a protein. Example: The lac operon in E. coli is a classic example of gene expression, where the presence or absence of lactose induces the expression of genes involved in lactose metabolism.
8. Regulation of Gene Expression: The mechanisms by which cells control the expression of genes, including transcriptional and translational regulation. Example: The trp operon in E. coli is regulated by a repressor protein that binds to the operator region, preventing transcription of the genes involved in tryptophan biosynthesis when tryptophan is present.
9. Operon:
A unit of genetic material in prokaryotes that consists of a promoter, an operator, and one or more structural genes, which are regulated together. Example: The his operon in Salmonella enterica is an example of an operon that regulates the expression of genes involved in histidine biosynthesis.
10. Gene Regulation:
The mechanisms by which cells control the expression of genes, including the regulation of transcription, translation, and post-translational modification. Example: The regulation of the SOS response in E. coli, which involves the coordinated expression of genes involved in DNA repair and replication in response to DNA damage.
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