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Evolution Notes

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Western University
Biology 3466B
Yolanda Morbey

Evolution NotesSept 2011 Evolution is descent with change in allele frequencies Individuals develop populations evolve DNA has a phosphate group attached to 5 end of 5carbon sugar and a nitrogenous base attached to 1 end of sugar nucleotide A and G are purines C and T are pyrimidines In the backbone of DNA a phosphodiester linkage forms between the 5 and 3 ends of adjacent nucleotides The bases stick out so theyre free to interact with other bases A and T have two hydrogen bonds between them while C and G have three Gene stretches of DNA that encode for a particular type of RNA or protein productLocus the location of the gene on a chromosome Allele alternative forms of a gene at a given locus Genotype characterization of the alleles carried by an individual Phenotype characterization of the traits expressed by an individual If there are two different alleles at the same locus it is a heterozygote Variation in alleles comes from mutations that occur during DNA synthesis Mutations can happen if the wrong nucleotide anneals to the template Most cells are in interphase but after DNA replication they enter prophase to begin mitosis In prophase there are replicated sister chromatids In metaphase they line up at the middle In anaphase they are pulled to the poles In telophase two daughter cells form In meiosis 1 homologous chromosomes form and separate In meiosis 2 the sister chromatids separate Mutations in the germ cell line affect fitness Mutations in somatic cells dont affect fitnessevolution Recombination reshuffles existing genes but doesnt create new genetic variation Two homologous chromosomes form a tetrad A chiasma forms between two chromatids and a synapse occurs at introns between the chromatids causes recombination The
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