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Genetic Engineering Chapter 16 – Population Genetics Population Genetics The study of microevolution Microevolution Change within species Occurs over hundreds of generations Macroevolution Occurs over long periods of time Origin of new species Gene Pool All genes of a local population of organisms Refers to the “frequency” of certain types of alleles Example – Plants Gene pools refer to ONE population, not an entire species They interbreed Polymorphism No two organisms are exactly alike Caused by differences in genes (alleles) If two or more alleles of a gene are present in a gene pool – population is POLYMORPHIC The butterfly Heliconius erato has multiple mimetic forms, controlled by many loci scattered at random among the chromosomes. Three of these forms are displayed here. The Hardy-Weinberg Model Idealized mathematical model of gene pools Many assumptions! Model predicts a relationship between allele frequencies and the expected genotype frequencies p = dominant allele frequency q = recessive allele frequency p+q=1 P2 = homozygous dominant Q2 = homozygous recessive 2pq = frequency of heterozygous dominant plants What’s the point? Use the allele frequencies to predict genotype frequencies Hardy-Weinberg Practice Problem Problem: 1 in 1700 US Caucasian newborns have cystic fibrous. C for normal is dominant over c for cystic fibrous. 1. When counting the phenotypes in a population why is cc the most significant? 2. What percent of the above population have cystic fibrous? Now calculate the expectant frequencies of all the following: Allele frequency (p and q) Frequency – homozygous dominant individuals? Frequency – heterozygous dominant individuals? An example of Hardy-Weinberg If 9% of an African population is born with a severe form of sickle-cell anemia (ss), what percentage of the population will be more resistant to malaria because they are heterozygous(Ss) for the sickle-cell gene? The Solution 9% =.09 = ss = q2 ()s = q = Square root of .09 = .3 p = 1 - .3 = .7 2pq = 2 (.7 x .3) = .42 = 42% of the population are heterozyotes (carriers) The Assumptions Highly idealized Assumes allele frequencies are the same over time Chapter 17 – Origin of Life Theory How did the universe form? Big Bang Theory Is the universe still expanding? Redshift Quiz – Earth Science Revisited How old is the Universe? How old is Earth? Big Bang occurred ~ 15 bya About 4.6 byo How did the Earth Form? Nebula Hypothesis Earth’s Early Atmosphere From volcanic gasses N2, CO2, H2O, H2, CO No oxygen! 1st organisms were anaerobic How did oxygen accumulate in our atmosphere? Photosynthetic organisms (3-3.5 bya) How did life begin on Earth? Which one is most widely accepted/easier to investigate? Life originated on some planet/star Life originated by unknown means on Earth Life evolved from nonliving substances through interaction with the environment Chemical Evolution Complex organic “soup” formed in oceans by: Energy sources Radioactivity Lightening Cosmic radiation Heat from volcanoes ORGANIC CMPDS formed Heterotroph Hypothesis (Oparin and Haldane) Need supply of organic molecules Process had to assemble molecules into polymers such as? Nucleic acids and proteins Other processes had to organize the polymers into a system that could replicate itself Urey-Miller Experiment Urey-Miller Experiment Urey-Miller Experiment 1950’s Recreated conditions like those 4.6 bya Water vapor circulated, cooled condensed Simulated gases, rain, lightening Small black tar; water was red Liquid contained organic molecules Urey-Miller Experiment Changed gases – CO2, water, nitrogen, hydrogen Made simple amino acids Recent experiments – 13 of 20 amino acids produced; ribose sugars Deep sea vents – organic molecule Eukaryotic Evolution Lynn Margulis Eukaryotes – originated as free-living prokaryotes Endosymbiont Hypothesis ENDOSYMBIONTS Symbiosis between large anaerobic prokaryotes and smaller aerobic or photosynthetic prokaryotes Why? Photosynthesis and aerobic respiration in small cells produced sugars benefited host cells Evidence – mitochondria have own DNA and ribosomes