Feb.25 Evolutionary Processes III

Feb.25 Evolutionary Processes III - Lecture 22: Feb. 25...

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1 Lecture 22: Feb. 25 Evolutionary Processes: Mutation, Genetic Drift & Gene Flow utation Discussion Activity after Winter Break Mutation translation - types of mutations - Lenski’s Experiment Genetic Drift -lab&f ie ldstud ies - under effects founder effects - genetic bottlenecks - nearly neutral theory Gene Flow Chapters 25 ( 443-450 ), 15 ( 279-287 ) Evolutionary Processes These are the processes that lead to changes in llele frequencies in a natural selection, sexual selection, genetic drift, ene flow allele frequencies in a population. gene flow, Most genes code for What is a gene ? A section of DNA that contains information for building a protein or RNA molecule. proteins. Many genes code for RNA molecules. A mutation is a change in an organism’s DNA. Mutation is the ONLY process that produces new alleles. Flow of Information: DNA to RNA to protein mRNA molecules connect DNA t i
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2 DNA to Protein: Genotype to Phenotype Genetic Code: each amino acid in a protein is specified by a group of three bases in mRNA. The Genetic Code has 64 possible 3 base combinations (codons) that collectively code for 20 amino acids and 3 stop codons . An amino acid typically has a number of “redundant” codons. MUTATIONS result from: errors in DNA replication - rrors in cell division errors in cell division The mutation rate in eukaryotes is generally 10 -4 to 10 -6 mutations per base pair per generation , and for bacteria the rate is around 10 -8 per base pair per generation. MUTATIONS result from: - errors in DNA replication e.g., replacement (=non-synonymous) substitution changes amino acid mRNA A change in a single nucleotide of DNA in gene that codes for hemoglobin changes just 1 amino acid in the hemoglobin protein but leads to a big change in phenotype of individuals who are homozygous for the mutant sickle cell allele. mRNA
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3 Types of POINT Mutations: errors in DNA replication MUTATIONS result from: - errors in DNA replication synonymous non-synonymous MUTATIONS result from: - errors in DNA replication rrors in cell division errors in cell division MUTATIONS result from: - errors in DNA replication - errors in cell division extra or missing pieces of chromosomes, inversions, extra or missing whole chromosomes, extra chromosome sets ype escription ause VOL Significance Type Description Cause EVOL. Significance chromosome inversion flipping of chromosome segment; order of genes is altered breaks in DNA caused by radiation/mutagens alleles in inversion are a “unit”; crossing over prevented in this region gene duplication duplication of short stretch of DNA; creates additional copy of gene unequal crossing over during meiosis “extra” gene copy is
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Feb.25 Evolutionary Processes III - Lecture 22: Feb. 25...

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