Lecture 10 - Virus Ecology I Flashcards Preview

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What are 4 statuses of viruses that are being debated about?

living or not, place on tree of life, how long they've existed, before LUCA?


Who discovered reverse transcriptase?

David Baltimore


What is one significant role of viruses that have a huge effect on all cellular organisms?

play a huge role in structuring microbial communities and populations


What are Pandora viruses?

giant viruses almost as large as cells (physically and genome-wise


What is the greatest source of biodiversity and most abundant biological entity on the planet?



What are 3 reasons why viruses are important?

helps in understanding an environment (microbiome) by looking at the virome; they are key components in evolution, important in medicine where vaccines have been made to different strains


Explain the theory that the eukaryotic nucleus comes from viruses

via "endosymbiosis" where an RNA cell during the RNA world gets infected by engulfing a primitive DNA and overtime, genetic info moved into the "nucleus"


What are 6 cellular functions people think that viral genes serve as a source for?

eukaryotic nucleus, transcription/translation machinery of mitochondrial genomes, proteins to form the immune system, embryo development, mammalian placenta formation, brain physiology


Explain the theory that viral genes provides proteins to form the immune system

viral proteins helps dampen the mother's immune response during pregnancy as the fetus is seen as a foreign mass of cells which the immune system would normally attack


Explain the theory of during embryo development and formation of the placenta that viral genes are expressed

people have found that the "junk DNA" in our genome are actually viral DNA that is expressed during the formation of the placenta and embryonic development


What is the simplest definition of a virus?

molecular intracellular parasite


What are 3 ways that viral genomes are diverse?

DNA/RNA; single or double stranded; (+) or (–) sense


What does a virus consist of?

nucleic acid that is surrounded by a protein coat (some with internal or external membranes)


In what other 2 ways (other then genomically) are viruses diverse?

different symmetries and morphologies


What is one big way that viruses are different than cellular life?

all viruses are dependent on cellular life for translation


What are the 2 ways how viruses are classified?

Baltimore and Hierarchal


Which classification system is more commonly used?



What are the 4 steps of the hierarchal classification system?

RNA or DNA | symmetry of capsid | presence or absence of envelope | architecture of genome: double-stranded or (+)/(–) single-stranded


What is the Baltimore classification scheme based off of?

how the virus makes mRNA


How many groups are there in the Baltimore classification scheme?



What are the 2 different types of viral replication cycles?

Lytic and Lysogenic (temperate)


What is the lytic cycle?

leads to cell lysis = release of progeny virions


What is the lysogenic cycle?

virus integrates its genome into host cell genome = whenever cell replicates, the viral genome gets replicated too and passed down to daughter cells


If the cell becomes stressed and launches a stress response, how will the lysogenic virus exit the cell?

virus is able to cut itself out and revert back to a lytic-cycle lifestyle


What is the effect of lytic viruses on the environment?

they will kill host after infection and can structure a population over a short period of time


What is the effect of lysogenic viruses on the environment?

has an effect on shaping the host population for a longer period of time since it will be maintained within the cell


In which type of environment are lysogenic viruses more prevalent in? (soil or aquatic)



In which type of environment are lytic viruses more prevalent in? (soil or aquatic)



How can the number of lytic viruses increase in any type of environment, soil and/or aquatic, and why?

if you add nutrients, lytic viruses will increase because if the cells are healthier = there will be more cells the virus can infect


When looking at the Virus-to-Bacteria Ratio, why is the viral population higher in soil than in water?

there are other organisms present in soil (such as fungi, plants, etc) therefore the soil is more rich in the amount of cells a virus can infect