Evolution Study GuideHIV- Azidothymidine (AZT)- interrupts reverse transcription; AZT used in place of thymidine- Reverse Transcriptase (of HIV)- uses viral RNA as template to construct a complementary stand of DNA Makes DNA using building blocks (nucleotides) stolen from the host cell- AZT Resistance is Heritable- What happens when AZT treatment is stopped? HIV w/out mutations are more efficient in reproducing in host cells that do NOT have AZT. Thus, stopping treatment favors non-mutant forms & proportion of different strains moves back in favor of pre-AZT treatment.- AZT did not cause HIV to become resistant. This variation (resistance) was pre-existing- Why weren’t HIV populations entirely resistant to AZT before the drug was introduced? There weren’t any selective pressures beforehand, so did not need the complete resistanceScience and Evolution- Science- method of inquiry that uses testable hypotheses to further understand reality- Characteristics of Science:1. Guided by Natural Law2. Explanatory by reference to a natural law3. Testable against empirical world4. Conclusions are tentative5. Falsifiable Creation Science FAILS to meet these so “not really a science”- Scientific Hypothesis:1. Falsifiable2. Guided by natural processes3. Conclusions are tentative4. Evidence leads to changes in a conclusion Science is evidence-based inquiry- Scientific Theory 2 Components:1. Observation of a pattern in natural world2. Underlying processes or mechanisms that cause that pattern Scientific Theory is supported by a large body of repeatable experimental evidence & facts- Evolution- change in frequency of gene/trait in population over multiple generations Descent w/ modification Change in inherited traits w/in a population over time Change in allele frequency from one generation to the next w/in population- Natural Selection- reproductive success over multiple generations (survival of the fittest)- 4 Bases for Evol. By Natural Selection:1. Individuals w/in species are variable2. Some variations are passed on to offspring3. Individuals that survive & reproduce are ones w/ most favorable variations survival & reproduction are NOT random- Effects of Evol. Visible at many scales: Persistence of a new mutation Change in frequency of allele Origin or loss of structures Origin or extinction of species- Macroevolution- large scale changes that lead to speciation or higher level diversification Large scale patterns in nature Homology1. Provides evidence of common ancestry: DNA = most widespread trait2. Represents similar design, but may have similar/different functions and/or appearance Vestigial Traits- useless structure w/ a function in a closely related species Pseudogene- gene that’s homologous to another gene in an allied species but lacks function usually result of mutation that stops transcription  Fossil Record- worldwide collection of fossils preserved Fossil record & carbon dating tell us that the earth = 4.6 billion years old Transitional forms- fossilized organisms that share traits of both ancestral & modern species Law of Succession- species change through time Extant & Extinct organisms share traits Fossilization NEED environment: Rapid burial, Anaerobic/No oxygen (slows decomposition), Non-acidic soil & little geologic activity Age of the Earth:  Life began 3.5 billion years ago Principle of Superposition- younger rocks lay on top of older rocks (relative dating) Relative dating use principle of stratigraphy Absolute dating use radioactive decay of unstable isotopes Rate of Decay: Constant; is NOT affected by environmental factors (water, heat, etc.) Radiometric Decay- parent isotopes are formed & lose particles to form daughter isotopes- Microevolution- small scale changes w/in population over time Underlying processes & mechanisms Direct observation of evolutionary changesMutation- Types:1. Nucleotide Pyrimidine = cytosine & thyamine Purines = Adenine & Guanine Complimentary base pairs: A& T, C& G2. ChromosomeDNA transcription mRNA translation Protein- How many Genes? Humans = 20000-25000  Smallest # of genes needed for living organism = 381- Point mutation: change in a single base pair Cause: errors in DNA replication or faulty repair of DNA Transition:1. A to G (purine to purine)2. T to C (pyrimidine to pyrimidine) MOST COMMON Transversion:1. Purine to pyrimidine2. Pyrimidine to purine- Insertion/Deletion: addition or loss of a base pair(s) Also known as frame shift mutations- Synonymous: base pair changes, but amino acid does not change Known as silent mutations Redundancy in the genetic code- Non-synonymous: base pair changes, resulting in amino acid change Mis-sense: changes in amino acid Non-sense: changes in stop/start codon Frame-shift: insertion/deletion of a base pair = both non-sense mutation- Chromosome Mutations:  Duplication/Deletion, Polyploidy, Inversion & Translocation Gene duplication- source of new genes Multigene families (e.g. globin genes) Polyploidy (Genome duplication)- duplication of entire sets of chromosomes Usual = 2N (diploid), Mutations = 4N (tetraploid), 6N, etc. Important/ common process driving plant evolution (rare in animals) Inversion- little effect if genetic material is NOT lost & genes are NOT disrupted Suppress recombination & prevent crossing-over Translocation- joining of non-homologous chromosomes- Transposable elements Transposons or jumping genes “Selfish DNA” that contributes to junk DNA Contains sequences that allows it to move around in the genome, usually leaving a copy of itself behind Recognizes specific sequences in DNA, cuts and inserts itself in there Can disrupt genes if it is inserted into a reading frameNumbers of mutations (different alleles) in a population reflects population size- Causes of Mutations: UV radiation (UV B the ozone hole, and skin cancer) Nuclear radiation Accelerated particles break DNA strands Organic solvents E.g intercalating agents, EMS, etc. Mistakes in DNA (spontaneous) DNA substitutions: replication, translation Mismatches: mitosis and meiosis- Whole Chromosome Mutations: Mosiacs1. Two genotypically different tissues within a single individual2. Multiple causes Nondisjunctions Failure of homologous chromosomes to separate in meiosis I