Bacterial Genetics & Regulation Lecture Vocabulary

Fifty vocabulary flashcards covering core terminology from bacterial genetics, DNA replication, gene expression, quorum sensing, and regulatory mechanisms.

Genome

The complete set of genetic information in a cell, consisting of the chromosome plus any plasmids.

Gene

A functional unit of heredity that encodes a gene product, usually a protein.

Plasmid

A small, circular, extra-chromosomal DNA molecule that replicates independently and often carries non-essential traits such as antibiotic resistance.

Bacterial Chromosome

The main circular DNA molecule of a bacterium that contains most essential genes.

Replicon

Any self-replicating genetic element possessing an origin of replication, including chromosomes and plasmids.

DNA Replication

The process by which a cell duplicates its DNA prior to cell division.

Semiconservative Replication

Mechanism in which each new DNA molecule contains one original (parental) strand and one newly synthesized strand.

Origin of Replication (oriC)

Specific chromosomal site where bacterial DNA replication is initiated.

DnaA

Initiator protein that binds DnaA boxes at oriC to trigger DNA strand separation.

Helicase

Enzyme that unwinds the DNA double helix ahead of the replication fork.

Primase

RNA polymerase that synthesizes short RNA primers needed to begin DNA synthesis.

DNA Polymerase III

Major bacterial DNA polymerase that elongates new DNA strands in the 5′→3′ direction.

Leading Strand

DNA strand synthesized continuously toward the replication fork.

Lagging Strand

DNA strand synthesized discontinuously as short Okazaki fragments away from the fork.

Okazaki Fragment

Short DNA segment produced during discontinuous synthesis of the lagging strand.

DNA Ligase

Enzyme that seals nicks by forming covalent bonds between adjacent DNA fragments.

DNA Gyrase

Topoisomerase that relieves supercoiling tension ahead of the replication fork.

Transcription

The synthesis of an RNA molecule from a DNA template by RNA polymerase.

RNA Polymerase

Multisubunit enzyme that catalyzes RNA synthesis and binds promoters with the aid of sigma factors.

Sigma Factor (σ)

Dissociable subunit of bacterial RNA polymerase that recognizes specific promoter sequences.

Promoter

DNA sequence upstream of a gene where RNA polymerase binds to start transcription.

Terminator

DNA sequence that signals RNA polymerase to stop transcription and release the RNA.

mRNA

Messenger RNA; transcript that carries codons specifying the amino-acid sequence of a protein.

rRNA

Ribosomal RNA; structural and catalytic component of ribosomes (16S, 23S, 5S in bacteria).

tRNA

Transfer RNA; adaptor molecule that delivers specific amino acids to the ribosome via anticodon-codon pairing.

Shine–Dalgarno Sequence

Purine-rich ribosome-binding site on bacterial mRNA that base-pairs with 16S rRNA to initiate translation.

Codon

Sequence of three nucleotides in mRNA that specifies an amino acid or stop signal.

Anticodon

Complementary three-nucleotide sequence on tRNA that pairs with an mRNA codon.

Genetic Code

Universal set of codon assignments that translate nucleotide sequences into amino acids; degenerate and non-overlapping.

Ribosome

70S prokaryotic translation machine composed of 30S and 50S subunits that synthesizes polypeptides.

Operon

Cluster of genes under control of a single promoter and regulatory elements, transcribed as one mRNA.

Polycistronic mRNA

Single mRNA molecule that encodes multiple proteins, typical of many bacterial operons.

Lac Operon

Inducible operon (lacZYA) for lactose metabolism regulated by Lac repressor and CAP-cAMP.

Repressor

DNA-binding regulatory protein that blocks transcription by binding an operator sequence.

Inducer (Allolactose)

Small molecule that binds Lac repressor, changing its shape so it cannot bind DNA, thus permitting transcription.

cAMP–CAP Complex

Activator formed when cAMP binds catabolite activator protein; enhances transcription of catabolite-sensitive operons.

Catabolite Repression

Global regulatory mechanism that suppresses alternate carbon source operons when glucose is present.

Quorum Sensing

Cell-to-cell communication system that regulates gene expression in response to population density via autoinducers.

Autoinducer (AHL)

Diffusible acyl homoserine lactone signal molecule used by many Gram-negative bacteria for quorum sensing.

LuxR Protein

AHL-binding transcription factor that activates quorum-sensing target genes once a critical signal concentration is reached.

Two-Component System

Signal transduction pair consisting of a membrane histidine kinase sensor and a cytoplasmic response regulator.

Histidine Kinase

Sensor protein that autophosphorylates on a histidine residue in response to environmental stimuli.

Response Regulator

Cytoplasmic protein that receives a phosphate from histidine kinase and modulates gene expression.

Alternative Sigma Factor

Sigma subunit that directs RNA polymerase to a distinct set of promoters during stress or developmental changes.

Stringent Response (ppGpp)

Stress response triggered by nutrient limitation; ppGpp reprograms transcription, slowing growth and conserving resources.

Antigenic Variation

Genetic mechanism in which pathogens alter surface proteins (e.g., Neisseria pilin) to evade host immunity.

Phase Variation

Reversible on/off switching of gene expression, such as pili expression in E. coli, enabling rapid adaptation.

Biofilm

Multicellular, surface-attached microbial community embedded in an extracellular matrix, often regulated by quorum sensing.

Pseudomonas aeruginosa

Opportunistic Gram-negative pathogen whose virulence and biofilm formation are heavily controlled by multiple quorum-sensing systems.

Genome Sequencing (Genomics)

Determination and analysis of complete DNA sequences of organisms to study structure, function and evolution.