Microbiology Exam 4 Part 2

Genetic elements that replicate independently of a cell's chromosome but require a living host in order to reproduce

Obligate intracellular

All

Acellular

DNA or RNA

Circular, double or single stranded, linear, or segmented

Virion

The complete virus particle

Nucleic acid surrounded by a protein coat and possibly external layers

10-2300 nm in diameter

Nucleocapsid

Nucleic acid (DNA or RNA) + protein coat (capsid) (some have additional components)

Complex, helical, and icosahedral

Protect the nucleic acid

Protein subunits that make up capsid

Virus RNA coiled and surrounded with capsomeres

Geometric shape

Binal and vaccinia

T4 bacteriophage

Has both helical and icosahedral symmetry

Genus and species

Helical

Negative sense and positive sense

Genome and mRNA are the same, plus strand, and positive

Genome and mRNA are compliments, negative, and negative strand

DNA => mRNA => protein

-RNA genome => +mRNA => protein

+RNA genome used as +mRNA or +RNA genome => -DNA => +mRNA => protein (retro viruses)

Flexible, membranous, outer layer

Host

Envelope proteins

Peplomers and spikes

Viral

Enzymatic activity, identification of virus, role in nucleic acid replication, and viral attachment to host cell

Animal (due to cell membrane and lack of cell wall)

Viral envelopes

Negative sense RNA virus

Viral structure of genome

Similar for all viruses

Attachment, entry, uncoating of genome, synthesis, assembly, and release

Latent period

Eclipse and maturation

Nothing is happening

Early enzymes, nucleic acid, and protein coats

Assembly and release before immune response occurs

Structurally complex and very diverse

dsDNA genomes

Naked

70% of marine prokaryotes

The ocean

Immediately after entering host

Virulent/lytic bacteriophages

Virulent/lytic bacteriophages

Remain within host cell without destroying it or reproduce as virulent phages (lytic pathway)

Temperate/lysogenic phages integrate genome into host genome

Temperate/lysogenic phages

Lambda

T4

Prophage

Nonlytic

Integrated bacteriophage genome

Integrase enzyme

Biotin and galactose operons (attachment site)

Infected bacterial host

As host genome replicates

Normal

The phenotype of its host

When a prophage changes the phenotype of its host

Switch from lysogenic to lytic cycle

Linear

double-stranded DNA

Process by which temperate/lysogenic phage reproduction is initiated

Switch to lytic cycle

Initiation of reproduction

Drop in levels of lambda repressor

Exposure to UV light or chemical mutagens that cause DNA damage

Binds to integrase enzyme and enables integrase to reverse integration process

Excisionase

Entire virion

Double-stranded DNA

Double-stranded DNA or single-stranded RNA

The nucleus of the animal cell

Enveloped

Cancer, latent, persistent, and virulent

Virus stops remaining stops reproducing and remains dormant for some time

Antivirus-antibodies, symptoms, and viruses are not detectable

Herpesvirus and varicella-zoster (i.e., chicken pox then shingles)

Virus infects cells and causes lysis (lytic pathway)

While unlikely, virus can repress tumor repressor genes so that tumors can grow

Clinical symptoms absent or mild for long periods, and virus almost always detectable

Hepatitis B and HIV

Viruses associated with human cancers

Accidentally

RNA viruses that replicate through a DNA intermediate

Enveloped viruses

Budding

Reverse transcriptase

RNA to DNA

HIV

Enveloped with club-shaped spikes, helical capsid symmetry, positive sense, and single-stranded RNA genome