Microbiology Test 3

Griffith's experiments on transformation

Demonstrated that genetic material could be transferred between organisms, transforming non-virulent bacteria into a virulent form.

Major structural differences between DNA and RNA

DNA is double-stranded, contains deoxyribose, and uses thymine; RNA is single-stranded, contains ribose, and uses uracil.

Phosphodiester bonds

Bonds that link nucleotides together in nucleic acids.

Origin of replication

Site where replication begins.

Replisome

Protein complex that facilitates DNA replication.

Replicon

Unit of DNA replicated from one origin.

Initiation phase of DNA replication

The phase where the origin of replication is recognized and helicase unwinds DNA.

Elongation phase of DNA replication

The phase where DNA polymerase synthesizes new strands.

Termination phase of DNA replication

The phase where replication ends when replication forks meet or at terminator sequences.

Leading strand

The DNA strand synthesized continuously during replication.

Lagging strand

The DNA strand synthesized in Okazaki fragments.

Okazaki fragment

A short DNA segment synthesized on the lagging strand.

Semi-conservative replication

Each new DNA molecule consists of one parental strand and one newly synthesized strand.

Key parts of a bacterial protein-coding gene

Promoter, coding region, and terminator.

Structure of bacterial RNA polymerase

Core enzyme with α, β, and β' subunits, along with a sigma factor for promoter recognition.

Initiation phase of transcription

The phase where RNA polymerase binds the promoter.

Elongation phase of transcription

The phase where RNA strand is synthesized.

Termination phase of transcription

The phase where RNA polymerase releases RNA at terminator sequence.

Role of bacterial promoters

Initiate transcription.

Role of sigma factors

Guide RNA polymerase to promoters.

Factor-independent transcription termination

Relies on RNA secondary structure for termination.

Rho-dependent transcription termination

Uses the rho protein to stop transcription.

Wobble hypothesis

Explains how the third base of a codon can vary without affecting the encoded amino acid.

A site during translation

tRNA brings in new amino acid.

P site during translation

Peptide bond forms between amino acids.

E site during translation

Empty tRNA exits the ribosome.

Role of molecular chaperones

Assist in protein folding.

Housekeeping genes

Genes that are always expressed.

Constitutive genes

Genes that are constantly expressed.

Inducible genes

Genes that are expressed in response to stimuli.

Repressible genes

Genes that can be turned off by specific signals.

Lac operon regulation

Regulated by lactose and glucose levels; lactose removes the repressor.

Trp operon regulation

Regulated by tryptophan levels; high tryptophan activates a repressor.

Spontaneous mutations

Mutations that arise naturally.

Induced mutations

Mutations caused by mutagens.

Types of DNA repair mechanisms

Proofreading, mismatch repair, excision repair, direct repair, recombinational repair.

F+ cells

Donor cells with an F plasmid.

Hfr cells

Cells where the F plasmid is integrated into the chromosome.

F' cells

Cells with an F plasmid that carries chromosomal DNA.

Generalized transduction

Transfer of random DNA by a phage.

Specialized transduction

Transfer of specific DNA near the phage integration site.

Five steps of a virus life cycle

Attachment, penetration, replication, assembly, release.

Antigenic drift

Minor mutations in viruses.

Antigenic shift

Major genome reassortments in viruses.

Prions

Misfolded proteins that induce normal proteins to misfold.

Creutzfeldt-Jakob Disease (CJD)

One of two human prion diseases.

Kuru

Another human prion disease.