Genetics – Microbiology Chapter 5 (Lecture Review)

Vocabulary flashcards covering key genetics concepts from Chapter 5, including genome organization, molecular processes (replication, transcription, translation), gene regulation, mutations, mutagens, and horizontal gene transfer mechanisms.

Genetics

The study of genes, their functions, and how variations arise in genomes.

Genome

The entire collection of genetic material (DNA or RNA) in a cell or virus.

Genotype

An organism’s complete set of genes that determines potential traits.

Phenotype

The observable traits or characteristics expressed by the genotype.

Chromosome

Carefully packaged strand of DNA associated with organizational proteins.

Histone

Eukaryotic DNA-binding protein that helps keep DNA untangled and organized.

Histone-like protein

Prokaryotic DNA-organizing protein analogous to eukaryotic histones.

Nucleoid

Region in prokaryotic cells where the chromosome(s) are located.

Plasmid

Small, extrachromosomal piece of DNA that often confers a survival advantage such as antibiotic resistance.

Nucleotide

Building block of nucleic acids composed of a phosphate group, deoxyribose (or ribose) sugar, and a nitrogen base.

Phosphodiester bond

Covalent linkage joining the sugar and phosphate backbone of nucleic acids.

Antiparallel arrangement

Orientation of the two DNA strands running 5'→3' and 3'→5' relative to each other.

Central dogma

Concept that genetic information flows from DNA to RNA to protein.

DNA replication

Is a process where a cell copies it genome before it divides

Origin of replication

Specific DNA sequence where replication begins.

Replication fork

Y-shaped region where parental DNA is unwound and new strands elongate.

RNA polymerase

Enzyme that synthesizes RNA from a DNA template during transcription.

Promoter

DNA sequence where RNA polymerase binds to initiate transcription.

Termination sequence

DNA sequence that signals RNA polymerase to stop transcription.

Transcription

First stage of gene expression in which DNA is used as a template to make RNA.

Reverse transcription

Process in which RNA is used as a template to synthesize complementary DNA (cDNA); requires reverse transcriptase.

Messenger RNA (mRNA)

RNA molecule that carries codons specifying the amino acid sequence of a protein.

Codon

Three-nucleotide mRNA sequence that codes for an amino acid or stop signal.

Transfer RNA (tRNA)

Clover-shaped RNA that carries a specific amino acid and contains an anticodon complementary to mRNA codons.

Anticodon

Three-nucleotide sequence on tRNA complementary to an mRNA codon.

Ribosomal RNA (rRNA)

RNA that folds with proteins to form ribosome subunits.

Ribosome

Cellular structure composed of rRNA and proteins that translates mRNA into protein.

Translation

Second stage of gene expression in which ribosomes synthesize proteins using mRNA.

Operon

Group of bacterial genes controlled by a shared regulatory region and transcribed together.

Operator

DNA segment in an operon where the repressor binds to block transcription.

Repressor

Regulatory protein that binds the operator to inhibit transcription.

Inducible operon

Operon that is OFF by default and activated under certain conditions (e.g., lac operon).

Repressible operon

Operon that is ON by default and can be turned off when the product is abundant (e.g., arg operon).

Lac operon

Inducible operon in E. coli controlling genes needed to digest lactose.

Allolactose

Inducer molecule that inactivates the lac operon repressor when lactose is present.

Arg operon

Repressible operon regulating synthesis of the amino acid arginine.

Quorum sensing

Bacterial communication system that tracks population density via autoinducers to regulate gene expression.

Mutation

Permanent change in a cell’s DNA sequence.

Substitution mutation

Mutation in which one nucleotide is replaced by another.

Insertion mutation

Mutation in which one or more nucleotides are added to the DNA sequence.

Deletion mutation

Mutation in which one or more nucleotides are removed from the DNA sequence.

Silent mutation

Base change that does not alter the encoded amino acid.

Missense mutation

Base change that substitutes one amino acid for another in the protein.

Nonsense mutation

Base change that converts an amino-acid codon into a stop codon, truncating the protein.

Frameshift mutation

Insertion or deletion that shifts the reading frame, altering downstream codons.

Mutagen

Chemical, physical, or biological agent that increases mutation rate.

Carcinogen

Mutagen that specifically increases the risk of cancer.

Ames test

Screening assay using his⁻ Salmonella strains to detect mutagenic compounds.

Horizontal gene transfer (HGT)

Transfer of genetic material between organisms without reproduction or cell division.

Vertical gene transfer

Transmission of genetic material from parent to offspring during reproduction.

Conjugation

HGT mechanism where DNA is transferred through a pilus from a donor to a recipient bacterium.

Pilus

Hollow, proteinaceous tube encoded by a fertility plasmid that facilitates conjugation.

Fertility (F) plasmid

Plasmid carrying genes for pilus formation and conjugative transfer.

Hfr strain

Bacterial cell in which the F plasmid is integrated into the chromosome, enabling high-frequency gene transfer.

Transformation

HGT mechanism in which bacteria take up free DNA from their environment.

Competent cell

Bacterium capable of taking up exogenous DNA during transformation.

Transduction

HGT mechanism whereby bacteriophages transfer DNA between bacteria.

Bacteriophage

Virus that infects and replicates within bacteria.

Generalized transduction

Phage packaging error in which random bacterial DNA fragments are transferred to another cell.

Specialized transduction

Phage-mediated transfer of specific bacterial genes adjacent to prophage integration sites.