Week 9 - Bacterial Genetics Flashcards
What is the basic structure of the bacterial chromosome?
Single circular molecule of double stranded DNA (dsDNA)
The chromosome is localized in the cytoplasm and anchored to the cytoplasmic membrane.
What does the term ‘genome’ refer to in bacteria?
The entire genetic content of an organism, including extrachromosomal elements like plasmids.
What are plasmids?
Small, circular extrachromosomal DNA that provides additional advantages such as antibiotic resistance
What is bacterial conjugation?
The process where plasmid exchange occurs between two competent bacterial cells.
What is the F plasmid?
A fertility factor which directs dna transfer to another bacteria via conjugation
What is rolling circle replication?
A process where the F plasmid makes a single-stranded copy of itself that passes into the recipient cell.
What are Hfr strains?
Formed when f plasmid integrates into the chromosome, enabling high-frequency recombination
What is homologous recombination?
The exchange of DNA sequences between different DNA molecules through highly similar sequences.
What role does RecA play in bacterial genetics?
Helps exchange genetic material between homologous DNA sequences and helps repair DNA
What are Holliday junctions?
Structures formed during homologous recombination where sequences on donor and recipient DNA are aligned and swapped.
What are R plasmids?
Vectors capable of carrying multiple antibiotic resistance genes.
What is transformation in bacteria?
The process where bacteria uptake fragments of DNA from the environment and incorporate it into their genome.
Who first observed transformation, and in what organism?
Prof Frederick Griffith observed transformation in Streptococcus pneumoniae.
What are bacteriophages?
Viruses that infect bacteria, consisting of nucleic acid surrounded by a coat of protein.
What is transduction?
DNA transfer mediated by bacteriophages
What are the two types of phage life cycles?
- Virulent phages
- Temperate (lysogenic) phages
What is generalized transduction?
Any bacterial gene can be transferred
What is specialized transduction?
A process where phages can only carry specific parts of the bacterial genome.
What is the purpose of mobile genetic elements?
To introduce new genes into a bacterial genome and mediate horizontal gene transfer.
What is the difference between vertical and horizontal gene transfer?
Vertical gene transfer occurs through reproduction, while horizontal gene transfer involves the exchange of genetic material between organisms.
What is the significance of mosaic structures in bacterial genomes?
Bacterial genomes evolve rapidly by integrating new genetic material from different sources.
What are mobile genetic elements?
Mobile genetic elements move genetic material between cells and mediate Horizontal Gene Transfer
Examples include plasmids and bacteriophages.
What is the difference between vertical and horizontal gene transfer?
Vertical gene transfer is the transmission of genetic material from parent to offspring, while horizontal gene transfer is the transfer of genetic material between organisms of the same generation.
How do bacterial genomes evolve?
Bacterial genomes evolve rapidly, with many species readily taking up and integrating new sections of genetic material into their chromosomes.
What is the structure of many bacterial genomes?
Many bacterial genomes are mosaic in structure, consisting of a mix of DNA segments acquired from different sources at various times.
Which bacterial species are highly clonal with limited DNA exchange?
Staphylococcus aureus and Mycobacterium tuberculosis are examples of species that are highly clonal.
What are genomic islands?
Genomic islands are newly acquired regions of DNA in bacterial genomes that often encode new traits providing a fitness advantage.
How is G+C content defined?
G+C content is the ratio of GC bases to AT bases in the genome.
What is the G+C content of Mycobacterium tuberculosis and Escherichia coli?
Mycobacterium tuberculosis has a G+C content of 66%, while Escherichia coli has a G+C content of 51%.
What are pathogenicity islands?
Pathogenicity islands are genomic islands involved in pathogenicity.
What distinguishes commensal E. coli K12 from pathogenic E. coli O157?
E. coli O157 has acquired a virulent phenotype through genomic islands compared to E. coli K12.
What does the outer circle in the genome comparison of E. coli K12 and E. coli O157 represent?
The outer circle shows areas of difference and similarity between the genomes of the two strains.
What does a G+C content of 50% indicate?
A G+C content of 50% indicates equal proportions of AT and GC bases.
What are the three processes by which bacteria can acquire new DNA?
The three processes are recombination, transformation, and transduction.
What is transformation in bacteria?
Transformation is the direct uptake of ‘free’ DNA from the external environment.
What is transduction in bacteria?
Transduction is the transference of DNA molecules via bacteriophages.
What is conjugation in bacterial genetics?
Conjugation involves close contact between bacterial cells, often mediated by F plasmids.
What role do mobile genetic elements play in bacterial evolution?
Mobile genetic elements can transfer genes between bacterial species by horizontal gene transfer events.
