Viral Infection and Genetic Diversity Quiz

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Questions and Answers

What is a virion?

The extracellular form of a virus that facilitates transmission

What is the main difference between naked viruses and enveloped viruses?

Enveloped viruses have an outer layer made of phospholipid bilayer and viral proteins

What is the defining characteristic of a virulent (lytic) infection?

Replicates and destroys the host cell

How are viruses classified based on the nature of their genetic material?

DNA or RNA genomes Signup and view all the answers

What is the function of virion surface proteins in viruses?

Important for host cell attachment and may include enzymes involved in infection/replication Signup and view all the answers

What is the primary requirement for a virus to multiply?

A living (host) cell Signup and view all the answers

Which step is not part of the replication cycle of prokaryotic viruses?

Maturation Signup and view all the answers

What is the primary function of lysozyme in virions?

Breaking down bacterial cell walls Signup and view all the answers

Which structure surrounds the nucleocapsid in enveloped viruses?

Lipoprotein membrane Signup and view all the answers

What is the role of burst size in the growth curve of viruses?

Number of virions released Signup and view all the answers

How are bacteriophages cultured, detected, and counted?

Plaque assay and animal cell culture Signup and view all the answers

What is the purpose of the head-plus tail structure in some bacteriophages?

Facilitate attachment to host cells Signup and view all the answers

What can be used to infer relationships between microbial species based on accumulated mutations since a common ancestor?

Nucleotide sequence differences between homologous genes Signup and view all the answers

What does >97% SSU rRNA sequence identity indicate?

The same species Signup and view all the answers

Which method can distinguish species that cannot be resolved by rRNA sequences?

Multilocus sequence analysis using protein-encoding genes Signup and view all the answers

What does whole genome analysis allow for in microbial ecosystems?

Reconstruction of metabolic/physiological characteristics and estimation of relatedness Signup and view all the answers

What does stable isotope probing involve in microbial communities?

Feeding microorganisms with labeled substrates to identify those utilizing specific compounds Signup and view all the answers

What do microbes account for in terms of biomass on Earth?

~50% Signup and view all the answers

What type of mutation in genes is more common, leading to loss of function?

Deleterious mutations Signup and view all the answers

In the long-term experimental evolution of E. coli, what change in fitness was observed initially?

Dramatic increase Signup and view all the answers

What resulted from a gain-of-function mutation in E. coli after 31,500 generations?

Ability to utilize citrate Signup and view all the answers

What role does gene duplication play in genome evolution?

Allowing one copy to evolve new functions while the other maintains the original function Signup and view all the answers

What type of genome dynamics do gene deletions contribute to in microbial genomes?

Maintenance of small microbial genomes Signup and view all the answers

What is the significant role of horizontal gene transfer in microbial evolution?

Allowing DNA transfer between distant evolutionary branches Signup and view all the answers

What is a characteristic of animal viruses?

They universally involve capsids and DNA/RNA genomes Signup and view all the answers

What is a feature of viral infection of animal cells?

It involves binding to specific host cell receptors and entry by fusion or endocytosis Signup and view all the answers

What is a characteristic of retrovirus integration into the host genome?

It involves reverse transcription and dsDNA integration into the genome by integrase Signup and view all the answers

What is a characteristic of influenza A virus?

It has a segmented genome Signup and view all the answers

What is a source of genetic diversity?

Mutation, recombination, and evolutionary selection Signup and view all the answers

What is genetic drift?

A random process causing gene frequencies to change over time Signup and view all the answers

Study Notes

Viral Infection and Genetic Diversity

Lysogeny is maintained by phage-encoded repressor protein, which, when inactivated, induces the lytic stage.
Animal viruses universally involve capsids, DNA/RNA genomes, infection, takeover of host, assembly, and release.
Differences between animal and bacterial viruses include host cell entry, eukaryotic cell nucleus involvement, and the formation of viroplasms in some eukaryotic cells.
Viral infection of animal cells involves binding to specific host cell receptors, entry by fusion or endocytosis, and uncoating at the cytoplasm or cytoplasmic membrane.
Outcomes of virulent infection include lysis of host cells, latent infection with viral DNA existing in the host's genome, persistent infection with slow virion release, and transformation of normal cells into tumor cells.
Retrovirus integration into the host genome includes HIV-1, an enveloped virion containing two copies of the ss (+) RNA genome, with reverse transcription and dsDNA integration into the genome by integrase.
Influenza A virus has a segmented genome, surface proteins interact with host cells, and antigenic shift can lead to major outbreaks.
Coronaviruses are enveloped viruses causing respiratory infections, including severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of COVID-19.
Genetic diversity originates from mutation, recombination, and evolutionary selection, with mutations occurring by chance and environment selecting for advantageous mutations.
Genetic drift is a random process causing gene frequencies to change over time, leading to evolution in the absence of natural selection, particularly impactful in small populations and those experiencing frequent bottleneck events.
Sequence changes can be used as a molecular clock to estimate time since a species diverged, with nucleotide changes accumulating in proportion to time and being generally neutral and random.
Experimental evolution uses microbes to investigate evolutionary processes, facilitated by their rapid growth and preservation through freezing, allowing for the observation of evolutionary events relatively quickly.

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