Cell Biology: Lytic and Lysogenic Cycles, Retroviruses, and Bacteriophages

Flashcards covering key vocabulary terms, structural components, and replication cycle stages for lytic viruses, lysogenic viruses, retroviruses, and T4 phage infections from Life Sciences 11 Cell Bio notes.

Lysogenic Cycle

A viral replication cycle in which the viral genetic material attaches to host DNA or a plasmid and lies dormant (inactive/latent) without immediately destroying the cell, replicating along with the host cell DNA during division.

Provirus

Viral DNA integrated into a eukaryotic host cell's DNA.

Prophage

Viral genetic material attached to a plasmid or integrated into a bacterial chromosome ($\text{Prophage} = \text{host DNA} + \text{viral DNA}$).

Lytic Cycle

An active, infectious viral cycle where a virus hijacks the host cell to make new viral nucleic acids and proteins, eventually lysing the cell to release new viruses.

Attachment

The initial stage of viral infection where the virus joins with or sticks to specific receptor sites on the host cell using structures like tail fibers.

Penetration

The stage of viral infection where the virus thrusts its core through the host wall/membrane and inserts its genetic material (nucleic acid: DNA or RNA) into the host cell.

Biosynthesis

The stage in a lytic infection where the host cell's metabolic machinery is directed by viral DNA to manufacture viral nucleic acids and viral proteins.

Maturation

The stage of viral infection where separate sets of viral proteins develop and assemble inside the bacterium to form complete new viruses (heads, tails, and tail fibers).

Lysis

The final stage of the lytic cycle where the bacterium wall is damaged, causing osmosis to swell and burst the host cell, releasing new viruses to infect more cells.

Retrovirus

An RNA-containing virus (such as HIV, influenza, or some cancer-causing viruses) that typically infects animal cells, follows a lysogenic pathway, and uses reverse transcriptase to create a DNA copy of its RNA genome.

Reverse Transcriptase

An enzyme used by retroviruses to produce a DNA copy from their RNA genetic code upon infecting a host cell.

gp120

Envelope proteins located on the outer lipid bilayer of retroviruses such as HIV.

p24

Capsule protein component forming the structural core inside retroviruses such as HIV.

T4 Phage

A specific bacteriophage that uses tail fibers to attach to receptor sites on an E. coli cell, contracts its sheath to inject DNA, and releases $100$ to $200$ phage particles upon host lysis.

Ghost

The empty viral capsid left on the outside of the host cell after a bacteriophage has injected its DNA into the cell.

Lysozyme

An enzyme directed by phage DNA during the lytic cycle that digests the bacterial cell wall to facilitate cell lysis.

Lysogenic Triggers

Environmental factors such as UV radiation, stress, or other illness that induce a dormant prophage to exit the bacterial chromosome and enter the lytic cycle.