Virology 3 Flashcards
What must all viruses make so they can be translated to proteins by ribosomes
must make mRNA
What is life
Independent metabolism & reproduction
What same metabolic pathways do all cells use
- Glycolysis
- Amino acid biosynthesis
- Electron transport
What common ancestor has already developed most of the biochemistry that we see in life today
Last Univeral Common Ancestor (LUCA)
Who created the Tree of Life
Ernst Haeckel
Tree of life: what did the braches represent
Different groups of organisms
Tree of life: what did the trunk represent
Common trunk that represents the origin of life
Why is Haeckel’s tree of life limited
It is oversimplified- shows linear progression of evolution with simpler organisms evolving to more complex organisms - not always the case
Whittaker’s tree of life
Living organisms grouped into 5 major kingdoms - Animalia, Plantae, Fungi, Protista, Monera
How is the Whittaker system also oversimplified
Doesn’t account for genetic relatedness of organisms - key aspect of modern phylogenetic classification
Carl Woese breakthrough
- Applied molecular techniques
- Targeted ribosomal genes to look at the relationship between organisms
- Ribosomal genes common to all life (have regions of variation) - encode ribosomes that make proteins
what 3 kingdoms did carl woese split organisms into
- Bacteria
- Archaea
- Eukaryota
how was the tree of live reconstructed - alignment of what?
The tree of life was reconstructed by aligning and linking a set of 16 ribosomal protein sequences from each organism
What appears do divide the Bacteria domain
CPR - Candidate phyla radiation
Why is Eukarya less prominent & less diverse of a domain than Bacteria & Archaea
Due to comparatively recent evolution
Why are viruses not on tree of life
- Not living
- Don’t encode ribosomes - not common biomarker
Key idea in RNA world hypothesis
- Life’s early origins may lie in RNA molecules
- Served as genetic material & had enzymatic avtivity
When did microbial cells first appear on earth
3.8 - 4.3 billion years ago
What can RNA do that DNA can’t in terms of replication
- DNA needs protiens & enzymes to replicate
- RNA can carry info & catalyse rxns (ribozymes) - RNA has all structural prerequisites for self replication
What is a possible evolutionary step that led to the first functional cell? in RNA world theory
Evolution of RNA protocells & RNA viruses
How did transition from an RNA based world to a DNA based world occur
Involved the emergence of enzymes capable of synthesising DNA from RNA templates - RdRP (RNA dependent RNA polymerase)
What is the virus first hypothesis
- Viruses predate cellular life
- Viruses emerged from simple organic molecules that were capable of self replication
- self replicating molecules similar to DNA /RNA
- viruses parasitised these self replicating molecules
- evolved mechanisms to improve replication & transmission - development of more complex viral structures
Evidence of virus first hypothesis
- Phylogenetics
- Predominance of RNA viruses & remnants of viral DNA in hosts
- in vitro experiments
What is the escape hypothesis
- viruses evolved from parts of genomes that escaped from cellular organisms
- parts of genome gained ability to move between cells
Evidence of escape hypothesis (2)
- Transposons
- Retrotransposons
what is the regressive (or reduction) hypothesis
- viruses are remnants of cellular organisms
- believed to have evolved from free living organisms that lost their function as they adapted to a parasitic life
- regressive evolution - reduction of genomes & loss of cellular machinary resulting in formation of viruses
Evidence of regressive hypothesis
- Mimivirues
- NCLDVs - nucleocytoplasmic large DNA viruses
Why was Mimivirus first thought to be a gram pos bacterium
Mimics cells in size and function
Genome size of Mimivirus
1.2 Mb (huge)
What cellular functions do mimiviruses have genes for
- Metabolism
- Translation
- DNA repair
Giant viruses often affect what
Amoeba - Acantahamoeba polyphaga
What environments are giant viruses usually found
Marine & extreme environments
