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first midterm bch447.docx

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University of Toronto St. George
Larry Moran

1-Read 2- Discuss neutral theory and what it means Present neutral mutations that have effects on phenotype Explain how phenotype can be overlooked What is neutral theory, the assumption is that although neutral mutations occur at the genetic level they are of no consequence if they are not phenotypically present. And furthermore, that if phenotype is involved than a mutation is under selective pressure. This is untrue, there are a meriad of neutral mutations giving rise to phenotypes without including selection... occurring through random genetic drift. The most obvious one being blood type. Therefore, the neutral theory does not only apply to mutations detected by molecular genetics... phenotypic alterations do not define selection and are not impermeable to random genetic drift. 3- The molecular clock ticks at different rates in different proteins based on their ability to mutate while conserving function Large sequence sectors not important for the function of the protein Small proteins largely composed of active site mutate less Loss off lethal mutants Abilities to buffer certain amino acid alterations without affecting active site function Codon repetitions in point mutations. 4- sequencing the fossils of related species can provide insight into the mutations that occur in genomes of that same species over time. As such, knowing when the organism died (by looking at the radioactive decay of the fossil) and aligning sequences for comparison to related organisms today can tell us how many mutations occur over what period of time. This allows us to then approximate the amount of time it takes to undergoe one mutation. Furthermore, it allows us to compare the mutation rates between species. 5- The lack of teaching may have to do with lack of understanding. But it is certain that population genetics is vital in the understanding of evolution. Effective population size. The potential to integrate an allele into the population (1/2ne). The amount of time it takes to fix the allele 4ne generations. The mutation rate per generation. And the fixation of the mutation rate being constant as a function of all the mutations. Meaning the rate of fixation is miu. 6- A gene is a functional nucleotide sequence. Whether it be to form protein, or rrna, or functional rna, and is subject to mutation. Different genes and different mutation rates... question 3 7- there is no difference from my point of view of a gene today to that of an introductory first year university textbook. A gene is a functional unit of the cell that manifests itself in either protein or functional rna. The other functions are related to the fnctions of the genome as a whole... as in all of the chromosomes and how for example they may regulate the expression of these genes. 8- find e coli... its the same. mutation rates are the same. selection pressures may be higher though. discuss selection pressures. 9- species trees are based on observable phenotypic traits, while gene trees are based on genomic comparisons and the relationships between genomes in terms of differences and similarities. 10- homologous, orthologous, paralogous? homology is the existence of shared ancestry between a pair of structures, or genes, in different species. Homologous sequences are orthologous if they are inferred to be descended from the same ancestral sequence separated by a speciation event: when a species diverges into two separ
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