All flashcards
Flashcard 1: Choose the expected recipient outcome: an F+ donor mates with an F− recipient and transfer completes.
Answer: Recipient becomes F+. Complete transfer of the F plasmid copy converts the recipient to a donor, promoting plasmid spread in the population.
Flashcard 2: Which option best defines a plasmid in prokaryotes?
Answer: Small circular extrachromosomal dsDNA that replicates independently. Plasmids provide genetic flexibility in prokaryotes by carrying accessory genes that can be horizontally transferred and replicated separately from the chromosome.
Flashcard 3: What is the term for a plasmid that can transfer itself between bacteria?
Answer: Conjugative plasmid. These plasmids encode transfer genes enabling self-propagation through conjugation between bacterial cells.
Flashcard 4: What does the F factor encode that enables conjugation?
Answer: Genes for sex pilus formation and DNA transfer (tra genes). These genes facilitate the formation of a conjugation bridge and single-stranded DNA transfer during bacterial mating.
Flashcard 5: Which option describes an F+ cell compared with an F− cell?
Answer: F+ contains the F plasmid; F− lacks the F plasmid. The presence of the F plasmid determines the donor capability in conjugation, distinguishing between donor and recipient cells.
Flashcard 6: What is the usual outcome for donor and recipient after F+ × F− conjugation?
Answer: Donor remains F+; recipient becomes F+. During conjugation, a copy of the F plasmid is transferred, allowing both cells to potentially act as donors afterward.
Flashcard 7: What is an Hfr cell in bacterial conjugation?
Answer: Cell with F factor integrated into the bacterial chromosome. Integration of the F plasmid into the chromosome allows transfer of chromosomal genes during conjugation.
Flashcard 8: What does Hfr stand for?
Answer: High frequency of recombination. This acronym reflects the enhanced rate of genetic recombination due to efficient chromosomal DNA transfer in conjugation.
Flashcard 9: Which DNA is transferred first during Hfr conjugation?
Answer: Chromosomal DNA adjacent to the integrated F origin of transfer. The origin of transfer site directs the sequential mobilization of DNA starting from the integrated F factor's position.
Flashcard 10: What is the most common F status of the recipient after Hfr × F− conjugation?
Answer: F− (transfer usually stops before the entire F factor enters). Conjugation bridges often break before the full F factor transfers, preventing the recipient from gaining donor capability.
Flashcard 11: What is an F′ (F prime) plasmid?
Answer: F plasmid that excised with adjacent chromosomal genes. Imprecise excision incorporates host DNA into the plasmid, enabling transfer of specific chromosomal genes via conjugation.
Flashcard 12: What is the term for transfer of bacterial DNA via direct cell-to-cell contact?
Answer: Conjugation. This process requires a sex pilus for cell contact and involves rolling-circle replication to transfer single-stranded DNA.
Flashcard 13: Which option best defines bacterial transformation?
Answer: Uptake of naked DNA from the environment by a bacterium. Competent bacteria can incorporate environmental DNA into their genome, facilitating genetic variation without cell contact.
Flashcard 14: What does it mean for a bacterium to be competent?
Answer: Able to take up exogenous DNA (naturally or artificially induced). Competence involves specific physiological states or treatments that enable DNA binding and uptake across the cell membrane.
Flashcard 15: Which option best defines bacterial transduction?
Answer: Transfer of bacterial DNA mediated by a bacteriophage. Bacteriophages package and deliver bacterial DNA during infection, enabling gene transfer between hosts.
Flashcard 16: What is the key distinction between generalized and specialized transduction?
Answer: Generalized: any gene; specialized: only genes near prophage site. Generalized involves random DNA packaging during lytic cycle, while specialized requires prophage excision carrying adjacent genes.
Flashcard 17: What is the term for movement of a DNA segment within a genome or between DNA molecules?
Answer: Transposition. This mechanism allows mobile genetic elements to relocate, contributing to genome evolution and antibiotic resistance spread.
Flashcard 18: What enzyme catalyzes movement of a transposon?
Answer: Transposase. Transposase recognizes inverted repeats and catalyzes cut-and-paste or replicative movement of the transposon.
Flashcard 19: Which option best defines an R plasmid in bacteria?
Answer: Plasmid carrying antibiotic resistance genes. These plasmids confer survival advantages in antibiotic environments by encoding resistance mechanisms like efflux pumps.
Flashcard 20: What is the major clinical significance of conjugative R plasmids?
Answer: Rapid horizontal spread of antibiotic resistance between bacteria. Conjugation allows quick dissemination of resistance genes across bacterial populations, complicating infection treatments.
Flashcard 21: What is horizontal gene transfer (HGT) in prokaryotes?
Answer: Gene transfer between organisms not via parent-to-offspring inheritance. HGT enables rapid adaptation by acquiring genes from unrelated organisms through mechanisms like conjugation or transformation.
Flashcard 22: Which process requires a bacteriophage: transformation, conjugation, or transduction?
Answer: Transduction. Bacteriophages act as vectors in transduction, unlike the direct contact in conjugation or DNA uptake in transformation.
Flashcard 23: Identify the transfer mechanism: uptake of free DNA by a competent bacterium.
Answer: Transformation. This mechanism relies on competent cells absorbing extracellular DNA released from lysed bacteria in the environment.
Flashcard 24: Identify the donor type: F factor integrated into chromosome and transfers chromosomal genes at high frequency.
Answer: Hfr cell. Integration of F into the chromosome enables high-efficiency transfer of linked bacterial genes during conjugation.
Flashcard 25: Which F status is produced when an F plasmid excises incorrectly and carries a host gene into the plasmid?
Answer: F′ (F prime). Aberrant excision merges plasmid and chromosomal DNA, creating a hybrid capable of specialized gene transfer.