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microevo.doc

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Department
Biology
Course Code
BIO3102
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All

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MicrobiologySynthetic theory of evolutionth20 century Huxley combined mendelian genetics and population geneticMust look at a large population in order to see evolutionWhat is MicroevolutionAllele frequencies traitswhere variation is occurringEvolutionary changes that result from changes in allele frequencies in a population or in chromosome structure or numbers due to mutation and recombinationLooking at actual source of variation and change within a population of a single speciesPopulationIncludes all the individuals of a single species that live together in the same place and timeGene PoolThe sum of all alleles at all gene loci in all individuals is called the populations gene poolGenotype frequenciesoratio of individuals possessing each genotype oEach diploid organism has 2 alleles for each traitAllele frequenciesoRelative abundance of different alleles in a population has to follow HW principles if want to calculate itNull hypothesisThe HardyWeinberg principle is a null model because it predicts what they would see if a particular factor had NO effectGenetic EquilibriumoNeither allele frequency or genotype frequency change in successive generationsIncomplete DominanceWhen the phenotype of both dominant and recessive are shown as a blendoEx not full red from dominant and full white from recessive but pink colour heterozygous PQAllele frequencies and Evolution HardyWeinberg Principle Null HypothesisMeasure of something not happening2 2Rule p 2pqq1 PP2Pqqq122use p and q to find allele frequencies p and qpredict what will come from what is already presentAa x Aa 121 AAAaaa genotypic ratioAa x Aa 31 dominantrecessive phenotypic ratiogenotype and phenotypegenotype is the genetic make up of the trait and phenotype is the appearance of the traitDominant Allele expressed in phenotype when more than one allele is present ARecessive Allele that is masked by a dominant allele aHomozygousState of possessing two copies of the same allele AAHeterozygousState of possessing two different alleles of a gene AaAssumptions For HardyWeinberg to workMicrobiology1No Natural SelectionoSelection changes allelic frequenciesif one of the alleles is not fit to survive and reproduce gametesallele is lost therefore cause microevolution If one allele has an advantage then over time it will increase is frequency causing fixationLoss or fixation of alleles lead to low diversity and variability CAUSED BY STRONG SELECTIONMouse ex they first allowed random mating of active and inactive mice mix of both in G1They then mated active with activeactive offsprings mostlyThey mated inactive with inactiveinactive offsprings mostlyoEffect of SelectionDarwin said Change is GRADUALwhat is the mechanismHardyWeinbergs rule probability theoryoFor Heterozygotes favouredIf heterozygotes favouredthe allele frequencies for heterozygotes will prevail in a populationOver time AA and Aa will even out to becoming equal and no aaSickle Cell Anemia Model for heterozygote selectionSingle Codon error in haemoglobin causes RBC to take a flat shapeNot in healthy donut shapedo not absorb enough oxygen respiratory stressaa die all from sickle cellno malaria not enough oxygenAA die all from malariano sickle cell malaria destroys all the cellsAa advantageous enough malaria and RBC to surviveWith Aa the Immune system picks up that the RBCs are damaged and it destroys those sickled RBCsoThe cells are infected with malaria so these get killed off with the sickle cellsOver time Aa becomes more prevalent in populationoSeen mostly in Africa where malaria thrivesAgainst Recessive Heterozygotes will prevailWhen we select against the recessive it will disappear and the frequency of the dominant allele will increaseheterozygotesoLoss of variationIf its all AA population then there is no effect All aa population they all die If its Aa population then 25 will die off and over time you will mostly have AASince most traits are polygenetic we need another method to know when there is a change and that is when we use the distribution curves mean is middle spread are the extremes standard deviation is the difference
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