Mutations & Mutants
A strain with a nucleotide sequence different from the parental strain.
mutant
Mutations that occur without external intervention
spontaneous mutations
The three main mechanisms of horizontal gene transfer
transformation, transduction, and conjugation
The state a cell must be in to take up DNA during transformation
competence
The cell that donates DNA during conjugation
F⁺ cell
A mutation that gives the organism a growth advantage under certain conditions
selectable mutation
A test that screens chemicals for mutagenicity using bacterial mutations
Ames test
The three possible fates of donor DNA after transfer into a recipient
degradation, replication, and recombination
A method that can artificially induce competence in bacterial cells
Ca²⁺ treatment or electroporation
The circular plasmid (~100 kb) that encodes transfer functions
F (fertility) plasmid
The experiment used to identify nutritional auxotrophs
replica plating
A DNA repair mechanism that directly reverses damage without needing the opposite strand
direct reversal
The protein essential for homologous recombination
RecA
Transduction where any portion of the host genome can be packaged into a phage
generalized transduction
The replication mechanism used during plasmid transfer in conjugation
rolling-circle replication
A mutation that introduces a premature stop codon
nonsense mutation
The repair pathway that removes bulky pyrimidine dimers caused by UV light
nucleotide excision repair
The physical structure formed during homologous recombination
Holliday intermediate (heteroduplex)
Transduction where only specific genes adjacent to the prophage site are transferred
specialized transduction
Cells with the F plasmid integrated into their chromosome
Hfr strains
A mutation at a different site in the DNA that compensates for the original mutation
suppressor mutation
The error-prone, damage-tolerant repair system activated by RecA and LexA degradation
SOS regulatory system
The selective medium used to detect recombinants in a tryptophan experiment
agar lacking tryptophan
The phenomenon when lysogeny alters the phenotype of the host
phage conversion
Why does the recipient cell in an Hfr conjugation event typically remain F⁻ instead of becoming Hfr?
Because only a portion of the F plasmid is transferred before mating ends