MCAT Biological and Biochemical Foundations of Living Systems Flashcards: 2b Viral Genetics Transduction Retroviruses

What this deck covers

This deck focuses on 2b Viral Genetics Transduction Retroviruses, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Biological and Biochemical Foundations of Living Systems.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the term for integrated retroviral DNA within the host chromosome?

Answer: Provirus. The integrated DNA form of the retroviral genome persists in the host cell and serves as a template for transcription.

Flashcard 2: What is transduction in bacteria?

Answer: Phage-mediated transfer of bacterial DNA between bacteria. Bacteriophages act as vectors, transferring bacterial DNA fragments from one bacterium to another during infection.

Flashcard 3: Which viral genome types must bring or encode an RNA-dependent RNA polymerase?

Answer: Negative-sense ssRNA viruses. Their genome cannot serve directly as mRNA, requiring polymerase to synthesize positive-sense RNA for translation.

Flashcard 4: What is specialized transduction?

Answer: Transfer of genes adjacent to prophage site after faulty excision. Faulty excision of prophage during induction incorporates nearby bacterial genes into the phage genome for transfer.

Flashcard 5: What is the enzyme that inserts retroviral DNA into the host genome?

Answer: Integrase. Integrase catalyzes the insertion of double-stranded viral DNA into the host chromosome during retroviral replication.

Flashcard 6: What is the term for the DNA copy of a retroviral genome made by reverse transcriptase?

Answer: cDNA (complementary DNA). Reverse transcriptase copies the retroviral RNA into a single-stranded DNA complement for integration.

Flashcard 7: What is the term for phage DNA integrated into a bacterial chromosome?

Answer: Prophage. During lysogeny, the integrated phage DNA replicates passively with the host chromosome without producing virions.

Flashcard 8: What is the key genetic consequence of reverse transcriptase for retroviruses?

Answer: High mutation rate due to low proofreading fidelity. Reverse transcriptase lacks 3'-5' exonuclease activity, leading to error-prone replication and rapid evolution.

Flashcard 9: Identify the key packaging error that causes generalized transduction.

Answer: Accidental packaging of host chromosomal DNA into phage capsid. In lytic infections, phage assembly errors lead to host DNA being encapsulated instead of viral DNA.

Flashcard 10: What is the defining feature of a virus regarding replication machinery?

Answer: Obligate intracellular parasite lacking independent replication machinery. Viruses require host cellular machinery for replication as they cannot independently synthesize proteins or generate energy.

Flashcard 11: What is the term for a bacteriophage that can integrate into the host genome?

Answer: Temperate phage. Temperate phages can undergo lysogeny, integrating their genome into the bacterial host's DNA without immediate lysis.

Flashcard 12: Which host enzyme typically transcribes an integrated provirus into viral mRNA?

Answer: Host RNA polymerase II. The provirus integrates into the host genome, utilizing the host's transcriptional machinery for viral RNA production.

Flashcard 13: What is the viral life cycle called when viral DNA persists in the host without killing it?

Answer: Lysogenic cycle. This cycle allows viral DNA to integrate and replicate with the host genome, maintaining a dormant state without cell death.

Flashcard 14: Identify the key excision error that causes specialized transduction.

Answer: Imprecise prophage excision that carries adjacent bacterial genes. During induction, imprecise cutting of prophage from host DNA includes adjacent bacterial sequences.

Flashcard 15: Which envelope acquisition mechanism is typical for enveloped animal viruses?

Answer: Budding through host membrane, acquiring a lipid bilayer envelope. Virions assemble at the plasma membrane and exit by budding, incorporating host-derived lipid envelope.

Flashcard 16: Identify the most likely transduction type if only genes near an attachment site transfer.

Answer: Specialized transduction. This type relies on imprecise prophage excision, limiting transfer to genes near the integration site.

Flashcard 17: Which transduction type can transfer any bacterial gene: generalized or specialized?

Answer: Generalized transduction. It involves random packaging of any host DNA segment into phage particles during lytic infection.

Flashcard 18: Which transduction type is limited to genes near the prophage insertion site?

Answer: Specialized transduction. It occurs only with temperate phages, transferring specific genes flanking the prophage integration site.

Flashcard 19: Which event converts a prophage from lysogeny to the lytic cycle?

Answer: Induction (prophage excision and entry into lytic replication). Environmental stressors trigger prophage excision, shifting from lysogeny to lytic replication and virion production.

Flashcard 20: Identify the most likely transduction type if many different host genes transfer randomly.

Answer: Generalized transduction. This type packages random host DNA fragments during lytic cycle, enabling transfer of diverse genes.

Flashcard 21: What is lysogenic conversion?

Answer: Prophage-encoded trait that alters bacterial phenotype (often toxin). Integrated prophage genes express proteins that modify host traits, enhancing bacterial virulence or survival.

Flashcard 22: Which viral structural component primarily determines host cell attachment specificity?

Answer: Viral surface proteins (capsid proteins or envelope glycoproteins). These proteins bind specific host cell receptors, dictating tropism and entry into susceptible cells.

Flashcard 23: What is generalized transduction?

Answer: Random bacterial DNA packaged into phage during lytic infection. During lytic cycle assembly, phage particles mistakenly package host DNA fragments instead of viral genome.

Flashcard 24: What is the immediate role of reverse transcriptase in retroviruses?

Answer: Synthesizes DNA from an RNA template. Reverse transcriptase uses the viral RNA genome as a template to produce a complementary DNA strand.

Flashcard 25: What is the viral life cycle called when virions are produced and the host cell lyses?

Answer: Lytic cycle. In this cycle, the virus hijacks host machinery to replicate, assemble virions, and cause cell lysis for release.