phage cycles and virus structures Flashcards
(23 cards)
What is the lytic cycle in phage replication?
A viral replication cycle that results in the destruction (lysis) of the host cell and the release of newly made viruses.
What type of phage only uses the lytic cycle?
A virulent phage.
What happens to the host cell’s DNA during the lytic cycle?
It is destroyed and replaced with viral genetic material, which hijacks the cell’s machinery.
What is the lysogenic cycle?
A phage replication cycle where viral DNA is integrated into the host genome and replicates without killing the host.
What is a prophage?
The viral DNA integrated into a host’s chromosome during the lysogenic cycle.
What type of phage uses both lytic and lysogenic cycles?
A temperate phage.
What can cause a prophage to switch to the lytic cycle?
Environmental signals such as stress or UV light.
How are animal viruses classified?
By type of genome (RNA or DNA) and by presence or absence of an envelope.
What are viral envelopes and their function?
Membranous coverings that contain glycoproteins which bind to host cell receptors, facilitating entry.
How are viral envelopes usually formed?
From the host cell’s plasma membrane, nuclear envelope, or Golgi apparatus.
Which type of viruses often have both an RNA genome and an envelope?
Animal viruses.
What is a retrovirus?
A virus that uses reverse transcriptase to convert its RNA genome into DNA.
What is a provirus?
A viral DNA permanently integrated into the host genome; it functions as mRNA to make viral proteins.
Why don’t viruses fit the definition of living organisms?
Because they cannot reproduce or carry out metabolism outside of a host cell.
What are possible sources of viral genomes?
Plasmids and transposons—mobile genetic elements.
How do viruses cause disease in animals?
By releasing lysosomal enzymes, producing toxins, or carrying toxic envelope proteins.
What does a vaccine do?
Stimulates the immune system by using a harmless form of a pathogen to prepare for future infections.
How do antiviral drugs work?
By inhibiting viral DNA synthesis or interfering with viral assembly; they do not cure infections.
How do plant viruses spread?
Through horizontal transmission (via damaged cells) and vertical transmission (from parent to offspring).
What kind of genome do most plant viruses have?
RNA genomes.
What are prions?
Infectious proteins that cause neurodegenerative diseases by misfolding and aggregating in the brain.
How do prions replicate?
By converting normal proteins into misfolded prions, which then aggregate and spread.
What diseases are caused by prions?
Mad cow disease, chronic wasting disease, and potentially Alzheimer’s and Parkinson’s.
