Bio 200 Lecture 7: Microevolution
Bio 200 Lecture 7: Microevolution
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Date Created: 09/15/14
Bio 200 Lecture 7 Microevolution and Mutations 1 Microevolution What causes evolution Population A group of individuals from a single species Genes are all the same but alleles differ Tongue rolling o Ability to roll RR or Rr 75 o Inability to roll rr 25 Allele frequencies A critical measure Allele frequency The number of times an allele occurs in the population Frequencies are represented as a proportion of the whole CG below are the driving forces of evolution Gene Flow The movement of alleles from one population to another Genes flow around as individuals and their gametes move among populations Evolution Allele frequency change Nonrandom mating Assortative mating Organisms of similar phenotype mate more often than expected by random change 0 As long as phenotypes are due to genotypes o Increases homozygotes decreases heterozygotes 0 Variation will go down due to lack of heterozygotes to add it Selffertilization causes variation to take a plunge due to no new genes being introduced Genetic Drift The Founder Effect o Population of lizards that can t swim 0 Near there there is a large river o These lizards lie on logs to warm o A few particular lizards on a log drift away from the population The log imbeds itself into another island with no other lizards 0 They thrive on the island 0 These founders founded a new population where there were no other individuals o This happens purely by chance not by selection o Evolution on the island will be different than on the original island allele frequencies will be different 0 Responsible for variation on the Galapagos I39JJI I I I39II39I 1 O original island allele frequencies will be different o Responsible for variation on the Galapagos Bottleneck Effect o Population of mixed phenotypes all is well o Natural disaster strikes population decreases dramatically o Survivors are a random collection of organisms 0 When population is brought back up allele frequencies will have changed 0 This works due to a constantly small sample size 0 The more individuals from the original populations the higher the representative the sample is o Survivors must be random or it becomes selection Mutation Not a major force Mutation rate is very small Typical gene mutates ever 100000 cell cycles o Most of these are incredibly minor Mutations themselves don t change allele frequencies themselves Mutation is the ultimate source of all genetic variability o Without mutation we would have no genetic diversity Francis Crick and Sydney Brenner o Determine how codons are read o DNA is the genetic material and proteins are made of amino acids 0 Found out that 3 nucleotides make up amino acids o The codes for amino acids are degenerate More than one codon can code for the same amino acid o Codons could be spaced by the nucleotides tha are notused Spaces seen as codons stopping or starting o OR That codons are put with no space between them Deletions o If spaced only disturbs one codon o But if not spaced skews all downstream codons o If the deletion is too large it is fatal Silent Mutations o Amino acid is not changed though base is Missense mutation o Change in a single base pair causes the substitution of a different amino acid in the resulting protein 0 May be neutral or harmful Nonsense mutation o Much more serious I l 1 IJJJ 1 J l Nonsense mutation o Much more serious o Lead to substitution for a stop codon o Stopping a strand early almost always leads to stop of protein function lnversions o Occur when a chromosome is broken in two placed reversed and stuck back in o As long as the cuts don t occur in the middle of a gene region they usually have no effect Translocation o Piece of a chromosome breaks off and attached to another chromosomes 0 Homologous pairs are no longer homologous o Organism is usually infertile Nondisjunction o Occurs when chromosomes fail to separate during Metaphase 1 Anueploids o Have gained or lost a chromosome o In humans these organisms do not survive o Common in sex chromosomes 5 of conceptions 51 00 o Kleinfelters Normal life usually not known of disorder o Turner s Syndrome XO Syndrome Only1 X chromosome Consequence free most of the time o Monozomy Loss of a single chromosome o Trizomy Addition of a single chromosome Trizomy 21 Down Syndrome Individual has normalclose to normal l espan 1750 humans have it Ploidy o Number of copies of chromosomes o Polyploidy more than two copies o Bananas come in many ploidy levels a 2N 22 o 4N 44 o 5N 55 o 7N 77 Four causes o Ionizing radiation o Chemical mutagens 0 Exposure to some viruses o Spontaneous mutation during replication Three outcomes o Harmful Lethal or minor to major effects o Neutral Silent occur in noncoding sections or no f nessloss Irarmrur Letnar or minor to major errects Neutral Silent occur in noncoding sections or no f nessloss Brown hair to blond hair Beneficial Change phenotype but improve individuals fitness The fuel that evolution runs on Very rare very powerful
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