exam 3 key evolution

exam 3 key evolution - Evolution BIO 370 Fall 2008 Exam#3...

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Evolution BIO 370 Page 1 Fall 2008: Exam #3 Name _____ KEY _____________________________ At the top of your exam, you’ll see that it is either a “3a” exam or a “3b” exam. I’ve broken down the multiple choice key below according each exam type. There were also differences between the 3a and 3b exams for the definitions. I’m sure you can figure out which of the definitions below pertain to your version of the exam. Part I : Multiple Choice. Exam 3a: 1: b; 2: f; 3: d; 4: f; 5: d Exam 3b: 1: f; 2: d; 3: d; 4: b; 5: f Part II : Definitions. All definitions were graded by Ginnie Morrison ! Cost of natural selection The additional death (beyond background mortality) imposed on a population as selection removes less fit genotypes and brings the alleles responsible for the favored phenotype to fixation. The cost of selection is the sum of the additional death in the population over all of the generations it takes to fix the favored allele. Important because Kimura used the concept to help him assess the relative importance of neutral and selective evolution in protein variation. ! Translational efficiency The rate at which a protein is translated from mRNA to an amino acid sequence. In our case, this was a function of how well the bias in synonymous tRNA types matched the bias in the same synonymous codons. Important for explaining why there is an observed codon bias, particularly in highly expressed genes. ! Peripheral isolate a small population that is geographically separated from a larger central population, either by changes in the range of the larger population or a founder effect. Important because this sort of population is one of the ways that allopatric speciation is thought to occur. ! Codon bias genes where the synonymous codons for the amino acids coded for by a gene are not all used approximately equally. [Instead the codons that match the most abundant tRNAs are more frequently used.] Shows that selection can act even among synonymous codons [or for biochemical biases/translational efficiency]. [May have mentioned: species specific .] ! Ring species a species that is geographically distributed along a cline that is arranged in space so that the opposite ends of the cline/distribution come back together. [The ring refers to the way the distribution of the species/cline circles back to itself.] Important because evidence from some ring species shows that the accumulation of microevolutionary changes can cause members of some species to genetically differentiate enough to stop interbreeding. ! Cline a situation where there is some aspect of the environment that changes over space, e.g., the fact that it gets colder as you move away from the equator. Important because clines can produce populations of an organism that vary along the cline due to selection. [Could mention some examples from class: sparrows, Streptanthus glandulosus, or the salamander Ensatia] ! Kimura 2-parameter model a model of DNA sequence evolution (substitutions) that has separate
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This note was uploaded on 08/24/2009 for the course BIO 370 taught by Professor Edwards during the Spring '08 term at University of Texas.

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exam 3 key evolution - Evolution BIO 370 Fall 2008 Exam#3...

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