Microbiology Exam 4: DNA Replication, Gene Expression, and Microbial Genetics

Comprehensive vocabulary flashcards covering microbial genetics, DNA replication mechanisms, gene expression, mutation types, and specific microbial pathogens.

DNA

The major genetic information storage molecule in all bacteria, archaea, and eukarya.

Messenger RNA (mRNA)

RNA molecules that serve as templates for the production of proteins during translation.

Griffith Experiment

An experiment that identified DNA as the genetic material by observing the transformation of non-pathogenic rough (R) strains into pathogenic smooth (S) strains in mice.

Transformation

A type of horizontal gene transfer where a cell takes up a free piece of DNA from its environment.

Avery, MacLeod, and McCarthy Experiment

Confirmed that DNA was the transforming factor by demonstrating that only DNases (enzymes that degrade DNA) eliminated the ability to alter phenotypes.

DNases

Enzymes that degrade DNA; used in experiments to confirm DNA is the hereditary material.

Hershey-Chase Experiment

Used bacteriophage T2 to prove that DNA, not protein, is the hereditary material injected into host cells during viral infection.

Nucleotide

A component of DNA consisting of a 5-carbon sugar (2-deoxyribose), a phosphate group, and one of four nitrogenous bases.

Nucleoside

A structure consisting of only a nitrogenous base connected to a sugar, without a phosphate group.

Purines

Nitrogenous bases containing a double-ring structure; includes adenine (A) and guanine (G).

Pyrimidines

Nitrogenous bases consisting of a single-ring structure; includes cytosine (C), thymine (T), and uracil (U).

Antiparallel arrangement

A double-stranded DNA configuration where the $5'$ end of one strand aligns with the $3'$ end of the complementary strand.

Complementary base pairing

The specific alignment of nucleotides where adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G).

Supercoiling

The twisting of circular DNA molecules to help compact their size within bacteria.

Plasmids

Small, circular extrachromosomal DNA molecules that typically contain non-essential genes.

Reverse Gyrase

An enzyme found in hyperthermophilic archaea that increases the thermostability of the chromosome.

Semiconservative replication

The process where each strand of the original DNA molecule serves as a template for a new strand, resulting in two DNA molecules each with one original and one new strand.

Origin of replication (oriC)

A specific sequence on the bacterial chromosome where DNA replication begins.

DnaA

A DNA binding protein in bacteria that binds to $9$-base pair repeats (DnaA boxes) to initiate strand separation.

Helicase (DnaB)

An enzyme recruited to the $oriC$ site to aid in the unwinding of the DNA double helix during replication.

Primase

An enzyme that synthesizes short segments of RNA needed to prime DNA replication.

Single-stranded DNA binding proteins (SSB)

Molecules that attach to newly formed single strands of DNA to prevent them from reannealing.

DNA polymerase III

The major enzyme in bacteria involved in synthesizing a new DNA strand by adding deoxynucleotide triphosphates to a free $3'-OH$ group.

Leading strand

The strand of replicating DNA that undergoes continuous elongation from the replication fork.

Lagging strand

The strand of replicating DNA that undergoes discontinuous elongation, necessitating multiple primers.

Okazaki fragments

Individual pieces of newly synthesized DNA and RNA primers on the lagging strand.

Replisome

A complex of proteins, including helicase, primase, and DNA polymerase, that allows for simultaneous synthesis of leading and lagging strands.

Telomerase

A DNA polymerase in eukarya that replicates and lengthens the ends of linear chromosomes (telomeres).

Transcription

The process by which segments of DNA serve as templates to produce complementary strands of single-stranded RNA.

Gene

A segment of DNA transcribed into single-stranded RNA along with associated DNA elements directing its transcription.

Promoter

A region of DNA where RNA polymerase binds to initiate transcription.

Sigma factor

The portion of bacterial RNA polymerase that recognizes the promoter sequence.

Rho-independent termination

Transcription termination involving inverted GC-rich repeats that form a hairpin structure, causing RNA polymerase to stall.

Rho-dependent termination

Transcription termination mediated by the rho factor protein binding to nascent RNA and displacing RNA polymerase.

Introns

Non-protein coding regions of a eukaryal gene that are removed during post-transcriptional modification.

Exons

Coding regions of a eukaryal gene that are spliced together to produce functional mRNA.

Codon

A group of three nucleotides in mRNA that specifies a particular amino acid.

Anticodon

A sequence of three nucleotides on a tRNA molecule that is complementary to an mRNA codon.

Shine-Dalgarno sequence

A segment of bacterial mRNA that binds to the $16S$ rRNA to properly align the mRNA on the ribosome.

Polycistronic

An mRNA molecule that codes for two or more different polypeptides; common in bacteria.

Monocistronic

An mRNA molecule that codes for a single polypeptide; characteristic of Eukarya.

Molecular Chaperones (Chaperonins)

Proteins, such as heat shock proteins, that aid in the correct folding of polypeptides.

Signal Peptide

A short stretch of hydrophobic amino acids at the N-terminus of a protein that serves as a 'postal code' for correct localization.

Missense mutation

A change in a nucleotide base that results in the substitution of a different amino acid in a polypeptide.

Silent mutation

A change in a nucleotide base that does not alter the amino acid sequence due to the redundancy of the genetic code.

Nonsense mutation

A change in a nucleotide base that results in the premature production of a stop codon.

Frameshift mutation

The addition or deletion of nucleotide bases that alters the reading frame of the entire DNA sequence.

Photolyase

An enzyme that repairs thymine dimers caused by UV light by cleaving the covalent bonds between adjacent thymine bases.

Auxotrophic mutant

An organism with a mutation that disrupts specific metabolic pathways, making it unable to synthesize certain amino acids or vitamins.

Replicon

A DNA molecule, such as a chromosome or plasmid, that replicates from a single origin of replication.

Plasmid incompatibility

The inability of two plasmids to exist stably within the same cell because they share the same replication control mechanisms.

Restriction enzymes

Enzymes that cleave DNA at specific short sequences called restriction sites, often used to create recombinant DNA.

Shuttle vectors

Plasmids that contain more than one origin of replication, allowing them to replicate in diverse types of host cells.

Horizontal gene transfer (HGT)

The movement of DNA between microbes, encompassing transformation, conjugation, transposition, and transduction.

Homologous recombination (Crossover)

A process where two DNA segments with highly similar sequences pair up and exchange portions of their DNA, mediated by RecA.

Conjugation

The specialized transfer of DNA from one cell to another via direct cell-to-cell contact, requiring the F plasmid.

Hfr strains

High frequency of recombination cells formed when an entire F plasmid integrates into the bacterial host chromosome.

Transposons

Mobile genetic elements that can move within and between genomes and may carry genes for antibiotic resistance.

Transduction

The transfer of bacterial DNA from one cell to another mediated by a bacteriophage.

Coxiella burnetti

The causative agent of Q fever; an obligate intracellular acidophile that exists in large and small variant forms.

Bartonella henselae

The causative agent of cat scratch disease; a gram-negative, slow-growing, fastidious aerobe.

Moraxella catarrhalis

A gram-negative diplococcus and opportunistic human pathogen that causes acute otitis media and respiratory infections.

Bifidobacterium breve

A gram-positive, non-pathogenic, forked rod-shaped bacterium found in the infant gut and used as a probiotic.

Anaplasma phagocytophilium

An obligate intracellular pathogen transmitted by Ixodes ticks that infects granulocytes and causes human granulocytic anaplasmosis (HGA).

BipA

A translational GTPase that functions as a stress response intermediary; it associates with $70S$ ribosomes under normal conditions and $30S$ subunits during stress.

ppGpp

A stress signal molecule (alarmone) that increases during starvation, causing BipA to bind to the $30S$ ribosomal subunit instead of the $70S$ ribosome.