Flashcards in Lecture 10 - Virus Ecology I Deck (64)
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?
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