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Evolution and Human Health.docx

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Biology 3466B
Yolanda Morbey

Evolution and Human Health Ch. 14 529-568 Flu virus evolves a million times faster than mammals Every year there are new strains of influenza that Objectives public officials must deal with Describe key events in the development of modern Officials must be able to predict these mutations in order to prepare vaccinations for the next season medicine Understand key features of influenza evolution Vaccines work by exposing patient to dead flue virus and immune system recognizes proteins as foreign Understand virulence and how it can evolve Apply adaptationist thinking to human health issues and mounts response against/remembers it Clinical Implications Origin of Modern Medicine Evolutionary biology and modern medicine were born The evolution is measures in nucleotide substitutions Flue strains accumulate nucleotide substitution in at the same time and have grown in parallel their hemma genes at a constant rate Louis Pasteur the germ theory of disease Mutations usually happen at the antigenic sites. Surviving lineages usually have the most amino acid Proposed that contagious diseases like cholera are replacements in its hemmaglutinin antigenic sites caused by germs 18 codons in the hemma gene have been shown to Cholera Outbreak, London 1854 have significantly more replacement substitutions These 18 codons have been under positive selection Epidemic which killed more than 500 people for changes in the encoding amino acids (mutations in Cause is unknown but linked to contaminated water these codons are critical) Scientists focus on sampling the strains at the 18 Joseph Lister; antiseptic surgery codons as the strain with the most mutations at these codons are likely to be currently circulating (survive) Alexander Fleming; discovery of penicillin First antibiotic medicine was penicillin, which Origin of Pandemic Flu Strains accelerated the decline in death rate Flues with novel hemma genes have selective Fundamental event in evolution is a change in the frequencies advantage in evading the hosts immune system. If of genotypes within a population. 2 kinds of populations they are able to radically restructure their hemma to whose evolution is important in medicine an new unknown strain they can cause a pandemic If 2 flu strain simultaneously infect the same host cell Populations of pathogens their genomes can recombined (swap genes) Populations of human cells within individual patients The structure of a strains nucleoprotein enables the strain to infect a particular species and confine strain Flue Virus Evolution to that specific species Clade a set of strains that are derived from a particular Influenza A is responsible for annual flue pandemics Has a genome composition of 8 RNA strands that common ancestor encode 11 proteins Each hemma group constitutes a clade Predominant coat protein is called hemagglutinin which is the primary protein recognized, attacked and H3N2 is H2N2 (human strain) which has traded genes with H3 (bird strain) and become a new type, this remembered by the hosts immune system To stay alive influenza must either find a steady caused the strain to cause a pandemic supply of nave hosts (never exposed) or alter its hemma Antigenic sites the specific parts of a foreign protein that the immune system recognizes and remembersEvolution and Human Health Ch. 14 529-568 How Does Virulence Evolve? 1. The coincidental evolution hypothesis Origins of 1918 Flu The virulence of many pathogens in humans may not be a Strain was isolated from a corpse of an Alaskan target of selection itself, but rather an accidental by-product of woman who died in 1918 selection on other traits Genes from this flu branch near base of clade that Virulence in the pathogen is a result of selection in a infects humans and pigs ie. common ancestor (1910) Implies all more recent human and pig strains are different environment, not within the host that the pathogen is currently in descendants of the 1918 flue or relative Most likely the 1918 strain came from birds (ultimate Tetanus is a disease that did not evolve within the flu strain reservoir) human population its a soil microorganism If tetanus gets into the bloodstream of humans it But there is no data on where the 1910 or 1918 strain came from produces a neurotoxin which can be lethal The lethality of tetanus is not due to the evolution within humans; it is a byproduct of its natural history Swine Flu in the soil environment Review Slides!!!!! 2. The short-sighted evolution hypothesis Thought it would become a pandemic so they wanted everyone to get vaccinated (not much hype about it Pathogens may experience many generations of evolution by this year) natural selection within one host before having an opportunity Birds brought H1N1 to swine to move to a new how. Results in, traits that enhance within- Human flu can infect pigs, Bird flue can infect pigs, Pigst fitness of strains rising to high frequencies, even if they flu can infect people are detrimental to transmission of path to new hosts. Popular hypothesis: pandemics begin when human
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