BIOEE 2780 Prelim 1 Answer Key (Spring 2008)

BIOEE 2780 Prelim 1 Answer Key (Spring 2008) -...

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Short Answer Questions 1. (10 points) Jean Baptiste de Lamarck and Charles Darwin both provided early theories of evolution. Briefly explain one way the theories were similar and one way in which they were different. Similar: Changes in inorganic and organic world results from operations of natural law, not miraculous intervention OR progressive change is from simple to more complex organisms Different: Lamarck theorized that new, simple organisms were created by spontaneous generation while Darwin suggested that all species descended from one or a few original species. OR Lamarck believed that inheritance of acquired characteristics was the mechanism of evolution and Darwin theorized that natural selection drives evolution 2. (14 points) The figure above represents a simple phylogenetic tree based on a particular nuclear gene. Taxa A and B differ at 8 nucleotide sites. Taxa C and D differ at 10 nucleotide sites. These four taxa are similar enough that the assumptions of a molecular clock are reasonable. (a) The divergence between A and B has been dated to 3 million years ago. What are two possible sources of this date? Fossil record or geological events (b) Use the information provided for A and B and the assumptions of a molecular clock to calculate the mutation rate for these taxa. Taxa A and B show 8 changes in 3 million years, or a rate of 4 mutations per lineage per 3 million years. Mutation rate = 4 mut/3 my = 1.3 mutations per million years . (c) Using the assumptions of a molecular clock, calculate the amount of time since the C and D lineages split. C and D differ by 10 nucleotides, so if we assume that were 5 per lineage and we get 1.3 mutations per million years, then we divide 5 by1.3 to get 3.76 million years ago. 3. (12 points) Name 4 types of point mutations. Identify the two types you expect to have the greatest negative impact on the fitness of the organism, and explain why. A B C D 8 differences 10 differences 3 million years ago
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Synonymous substitutions—a change in a single base pair that has no effect on protein amino acid sequence Nonsynonymous substitutions—a change in a single base pair that does cause a change in the amino acid sequence Nonsense mutations—a change in a single base pair that creates a stop codon Frame-shift mutations—these are insertions and deletions that are not in multiples of 3 Nonsense and frameshift mutations would be the most negative. Nonsense mutations would cause the entire protein not to be produced, and frame-shift mutations mean every codon is different so probably the protein would not be formed. Since most proteins serve a function in an organism, if one is not produced it is usually bad. Duplications and inversions are not point mutations.
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BIOEE 2780 Prelim 1 Answer Key (Spring 2008) -...

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