Bacterial Transformation and Plasmids Vocabulary

A complete set of vocabulary flashcards covering the history of bacterial transformations, plasmid structure, operon transcriptional regulation, pGLO, shuttle plasmids, transformation techniques, and plasmid purification.

Bacterial Transformation

A process discovered by Frederick Griffith in the 1920s showing how bacteria can obtain genetic information directly from other bacteria.

Bacterial Conjugation

A process discovered by Joshua Lederberg and Edward Tatum in 1946 in which bacteria transfer DNA directly between two cells.

Transduction

A mechanism discovered by Joshua Lederberg and Norton Zinder in 1951 where bacteriophages transfer DNA from one bacterium to another.

Plasmids

Extrachromosomal, self-replicating circular double-stranded DNA molecules found in bacteria.

Restriction Enzymes

Specific enzymes discovered in the late 1960s that cut DNA at specific nucleotide recognition locations.

Multiple Cloning Site (MCS)

A region in engineered plasmids containing unique restriction enzyme recognition sites used to cut open the plasmid and insert target DNA.

Origin of Replication (ori)

A specific sequence on a plasmid required so DNA polymerase can bind to recognition sites and replicate the plasmid.

Copy Number

The average number of a specific plasmid present per bacterial cell, typically ranging between 5 to over 1000 plasmids per cell.

R Factors

Plasmids carrying antibiotic resistance genes that bacteria pass down to convey resistance against specific drugs.

Constitutive Genes

Genes that are expressed continually and constantly by cells at all times.

Facultative Genes

Genes that are transcribed and expressed only when needed by the cell under specific conditions.

Operon

A naturally occurring prokaryotic gene control unit consisting of one promoter, an operator, multiple structural genes, and a single terminator that produces a single mRNA molecule encoding multiple proteins.

Repressor Protein

A regulatory protein that binds to the operator region near an operon and physically blocks RNA polymerase from transcribing.

Inducer

A molecule (such as lactose or arabinose) that binds to a repressor protein to alter its shape and relieve the transcriptional block on an operon.

pGLO Plasmid

An engineered plasmid containing the green fluorescent protein (GFP) gene, an ampicillin resistance gene, and the $araC$ repressor, causing transformed bacteria to glow under UV light in the presence of arabinose.

Shuttle Plasmids

Plasmids designed with specific origin and promoter features to replicate and express genes in two different host cell types, such as E. coli and yeast.

Ti Plasmid

A tumor-inducing plasmid originating from Agrobacterium tumefaciens that causes Crown Gall disease by integrating a segment of its DNA into a host plant's genome.

Transformation Efficiency

A calculated measure of the number of transformed bacterial colonies generated per microgram of plasmid DNA used, expressed in $\text{CFU}/\mu\text{g}$.

Calcium Chloride Transformation

A chemical transformation method where bacterial cells are washed in an ice-cold $\text{CaCl}_2$ solution to make them competent, followed by alternating heat and cold pulses to insert plasmid DNA.

Electroporation

A transformation technique that applies a high-voltage electrical pulse to temporarily disrupt cell membranes, creating pores through which plasmid DNA can enter.

Biolistics

A transformation method using high-pressure gas (such as helium) to shoot microprojectiles of gold or tungsten coated with DNA into plant or eukaryotic cell walls.

Blue-White Screening

A selection technique using the $lacZ$ gene and X-gal where recombinant colonies with disrupted $lacZ$ genes appear white, while non-recombinant colonies with intact $lacZ$ genes turn blue.

Pellet

The solid mass of bacterial cells or precipitate collected at the bottom of a tube after centrifugation.

Supernatant

The liquid layer remaining above the solid pellet following centrifugation.

Relative Centrifugal Force (RCF)

A unit expressing the centrifugal force exerted on a sample relative to Earth's gravitational acceleration ($g$), calculated using $\text{RCF } (g) = (1.12 \times 10^{-6})(s)^2 r$.

DNA Quantitation

The laboratory measurement of DNA concentration and purity in a sample using methods such as gel analysis, spectrophotometry, or fluorometry.