BIOA01-- Lecture 03 - EVOLUTION Hardy-Weinberg and the Agents of Evolution(chapter 21 RECAP Genetic variation is at the heart of evolution Variation can

BIOA01-- Lecture 03 - EVOLUTION Hardy-Weinberg and the...

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EVOLUTION: Hardy-Weinberg and the Agents of Evolution (chapter 21) RECAP: - Genetic variation is at the heart of evolution - Variation can be assessed both quantitatively and qualitatively - Can measure evolution as changes in allele frequencies in populations - POPULATIONS evolve, not individuals - [Ladybugs with opposite colored spots represent qualitative variation (distinct visual traits that can be categorized)] Considerable Genetic Variation in Populations: 2 EXAMPLES OF ARTIFICIAL SELECTION → Dogs & Brassica (plant → cabbage, broccoli, cauliflower, etc) Q: How do we assess this genetic variation? How can we use this variation to understand evolution? Assessing Genetic Variation: - Can assess observable phenotypic variation easily when genotype = phenotype (i.e. mendel’s peas, snapdragons) - Can measure genetic variation DIRECTLY (many cheap and high-throughput methods, many based on PCR) 1. Through GEL ELECTROPHORESIS (refer to diagram in lec 03) - Flies produce an enzyme called ADH, fruit flies feed on yeast that ferment fruit. ADH prevents the flies from becoming drunk when they feed on the yeast. This gene can be used to assess variation within the population. - Samples can be taken from different flies and put in gel, separated by size (smaller sized genes/dna will move faster towards the other [+] end) - After it has run for an hour or two, the genes will be stained with something that picks up the ADH enzyme. - Versions of ADH can not be assessed using phenotypes; all flies will look the same on the exterior. However, using this method you will be able to assess this genetically. [Homozygous allele 1, homozygous allele 2, heterozygous] POPULATION GENETICS -- populations are made up of individuals of the same species (each with their own genotype) that live in the SAME place and interbreed, producing FERTILE offspring - For evolution to occur, individuals in a population must differ genetically (however not all populations are evolving)

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