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Shape of the Day • Quiz: Structure of DNA • Agents of Evolutionary Change Notes • The Evolution of the Smartie • **Hand in Yeast Lab Write ups*** Review… • DNA carries the hereditary information • Double helix – Sugar-phosphate backbone – Nitrogenous bases • Provides the code to make all of the proteins that make up the organism Agents of Evolutionary Change Biology 11 • Allele-a different form of a particular gene • Example: Genes for flower colour: purple allele vs white allele Mutation • A change in the sequence of DNA • Mutations can occur when – There are errors when DNA is copied – There is exposure to mutagens (chemicals or radiation) • Changes to the genetic code lead to different traits arising • If the DNA changes the germ line (gametes), offspring will have same mutation • Changes to somatic cells will not pass on (somatic are all other cells) • Mutations can lead to… – No changes in phenotype (physical traits) – Small changes – Big changes • Mutations are random • Mutations can be beneficial, neutral, or harmful for the organism Mechanisms of Change 1. Mutation –New genes can become more frequent in population –Ex. Parents with genes for green colouration have a offspring with genes for brown colouration • Example: Peppered Moth • Which would be better able to survive and reproduce in their habitat? 2. Gene Flow (Migration) • Movement of genes from one population to another 3. Genetic Drift • Change in frequency of an allele • Each generation some individuals leave behind more offspring than others 4. Non-Random Mating • Probability that two individuals in a population will mate is not the same for all possible pairs of individuals. • http://www.youtube.com/watch?v=p9zK d3dfz8I • http://www.youtube.com/watch?v=U89t w093s_Y 5. Natural Selection • the process whereby organisms better adapted to their environment tend to survive and produce more offspring