University at Buffalo Lecture 11 Evolutionary Biology Based on Dr Poulin s Lectures Life has two characteristics 1 Organized 2 Replicates Itself Lots of Scientists find it hard not to treat viruses like living things Some scientists argue viruses aren t alive because they require a host Viruses are highly organized even though they aren t cellular organisms Use the same kind of genetic storage as living things Replicate With help Mutate Evolve Open question as to whether or not they are alive Facts of viruses o Have a protein coat aka Capsid o Inside Capsid is a care of nucleotides o Nucleotides are informs of DNA or RNA never both Animals have both o Circular or linear genetic material o Single stranded or double stranded Virus particles are not cells o No cytosol o No plasma membrane o No other cellular structure to identify as cells Viruses are definitely not cells Individual virus particles are called Virions o Virion Individual virus particle University at Buffalo Viruses are highly organized very recognizable Can t replicate genetic material on their own o Require host cells to replicate their genes for them Calls into question whether or not they are alive Viruses do evolve independently of other organisms o Respond to selective pressure from host as well as the outside world Viruses come in many shapes and sizes o Viral shapes Helical Capsid Helical capsule within envelope Icosahedral Capsid Icosahedral head Helical tail Almost all viruses have an overall shape either in 1 of 2 forms University at Buffalo o Helical o Icosahedral Icosahedron geometric solid with 20 equilateral triangular facets Maximizes internal capacity of the structure without dramatically increasing size holds more in less space Complex Viruses are binal binal shape Like binary two o Have both Icosahedral and helical element Virus size is highly variable o Ex Bacteriophage is only 4 times the size of a single hemoglobin protein o Virus size does not affect how dangerous they can be to host Virus replication is parasitic University at Buffalo o Infection is how viruses replication DNA instructs the cells machinery how to make proteins required for cellular functioning o Virus genome is another set of instruction that tricks the host cell into replicating the virus therefore making copies of the viral genome Producing viral capsid proteins so viruses can be made and infect other cells This process often destroys the infected cell while its happening Reproducing a virus 1 Virus tricks host cell into letting it enter the cell body 2 Substances in the cell begin to strip off the viruses outer coast of protein Natural process 3 Nucleic acids from center of virus get released because of this 4 The nucleic acids get into the cells chemical manufacturing system Usually through the nucleus 5 Causes cell to ignore own chemical needs then cell switches over to making new 6 Cell is usually destroyed in the process new viruses released by cell bursting open viruses Cell Lysis Common Transmissible Spongiform Encephalopathies TSE s o Not much to do with viruses or bacteria o Disease involved in this are fatal brain diseases Brains of infected individuals develop many small cavities where individual neurons have died University at Buffalo Brain turns spongy as more cavities form o Used to be called slow viruses Reason being often decades pass between time of infection and when the disease can be detected Transmission Vectors After infected neural tissue is injected into a healthy animal TSE s aren t viruses because they are actually Prions o Prions contain no genetic material TSE s remain active even after radiation that would destroy genetic material They have no DNA or RNA o Infections are passed by proteins only Prions are misfolded versions of normal proteins found in organisms susceptible to TSE s o When a normal protein comes in contact with a Prion it changes conformation o These abnormal Rogue proteins are exact same chemicals as normal ones but into the abnormal prion form in different shapes o The forcing of a normal prion is the equivalent of transmission infection o Misfolded prions are very resistant to degradation Prions stay in the body of the infected organism without going through the natural process of being degraded Therefore can spread the abnormal configuration to any other normal protein coming into contact o What causes degradation of brain cells Viruses and prions can deeply affect other lifeforms o Critical to understanding life around us o Excellent sources of evolutionary data Taxonomy doesn t always equal phylogeny o Very important to understand University at Buffalo o Each of these three domains are monophyletic In this old tree Protista are paraphyletic These tips are not equal The three domain tree is a better model to focus on University at Buffalo The tree of life might be changing again o Archean s and Eukarya aren t all equally related Eocytes and Eukarya share an II amino acid insert in a protein called EF1 Alpha o Protein is important for transcription Transcription binds TRNA to Ribosomes o With current tree that insert would have to occur twice Parsimony forces us to consider that Eukaryans branched out of the Archean group See above Picture This is the more likely to have happened So instead of three major groups Bacteria Archea and Eukarya you now only would have two Eukaryans would be highly specialized Archean Prokaryotes are fundamentally different 1 Unicellular 2 Binary Fission 3 Un enclosed DNA circular chromosomes 4 No Organelles 5 Asexual o Bacteria and Archea don t divide by mitosis like Eukarya they use Binary Fission o Don t have organized DNA so no nucleus Single ring shaped chromosome that floats in the center of the cell o No membrane bound organelles Some do have specialized infolding of plasma membranes University at Buffalo Some have photosynthetic membranes Both very similar to ones in Eukaryotes o NO regular predicable exchange of genes Biggest most defining feature of this group Lack of sexuality These differences define Eukaryotes 1 Multicellular 2 Compartmentalized Have organelles 3 Sexual Mostly o Still a lot we don t know about eukaryotic tree The eukaryotic tree o Plants Ch 28 29 o Fungus Ch 30 o Animals Ch 31 33 o Other tips Protists Basically the motley crew of the Eukaryotes Very much a catch all for all the organisms for small and other that didn t Protist name is misleading fit with other Eukaryotes Some are more closely related to plants fungus