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Biology 336 - Pre-tutorial Assignment #3

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University of British Columbia
BIOL 336
Greg Bole

Pre-TutorialAssignment #3 BIOL 336 Section 202 Cassandra Chan 60463080 January 25 , 2013 1. Selection acts directly on phenotypes, as it is phenotypic variation that creates differences between survival rates and reproductive success of individuals. However, phenotypes are a result of genotypes interacting with the environment; and genotypes are combinations of alleles. Therefore, selection acts indirectly on genotypes and alleles. 2. An allele does not have a phenotype on a diploid organism because diploid organisms require at least two alleles of a particular gene; even then, an expression of one particular gene does not necessarily give rise to a phenotype. Phenotypes are usually a combination of different alleles and their interactions with the environment. In haploid organisms, it is possible that a single allele may be responsible for a particular phenotype if it is the only other allele in a population of haploid organisms that shows a difference in phenotype. 3. Run 1 Run 2 Run 3 w11 1.22 1.22 1.22 w12 1 1.22 1.11 w22 1 1 1 Colour Red Orange Yellow-Green Fitness Effect Recessive Dominant Additive Reasoning Since we set the population size to be infinite, we eliminate the probability of genetic drift occurring. In Run 1, w11 is 1.22 so has an advantage over A1A2 andA2A2 genotypes. However this phenotype is recessive, requiring 2 copies of alleleA1. Therefore the number ofA1 alleles is low in the beginning and most likely found in heterozygotes.AlleleA1 rapidly increases once drift or some mechanism increases their frequency slightly, and then selecti
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