2010Exam-two-Crib

2010Exam-two-Crib - PRINCIPLES OF EVOLUTION(Fall 2010 CRIB Name Second Exam(1 April 2010(1 Imagine a gene coding for some protein The wildtype

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PRINCIPLES OF EVOLUTIO N (Fall 2010) ___________ CRIB _____________ Name 1 Second Exam (1 April 2010) (1) Imagine a gene coding for some protein. The wildtype allele is A (below), and in separate events, mutates to a pair of additional alleles, B (10 th codon mutation) and C (139 th codon mutation). We now have three alleles in the population, though B and C have low frequency. _____DNA_____ ________Protein_______ ( 10 TAT --- 139 AGC ) RNA [ --- Ile --- --- Ser --- ] B ( 10 GAT --- 139 AGC ) RNA [--- Leu --- --- Ser --- ] A ( 10 GAT --- 139 ACC ) RNA [--- Leu --- --- Trp --- ] C (a) Several generations later, we can get a recombination within the confines of this gene, somewhere between codons 10 and 139. Indicate the meiotic products of such intra-genic recombination in the table below, along with their relative frequencies (8 points). (b) Two Alleles Involved Meiotic Products Two Alleles Involved Meiotic Products A with A all A A with B (½A) , (½B) B with B all B A with C (½A) , (½C) C with C all C B with C (¼A) , (¼B) (¼A) , (¼B) (c) Remembering that crossing over occurs at the four-strand stage of Meiosis, diagram what happens with intra-genic recombination of B and C (9 points). B [ --- Ile --- --- Ser --- ] B [ --- Ile --- --- Ser --- ] ¼ B [ --- Ile --- --- Ser --- ] A [--- Leu --- --- Ser --- ] ¼ C [--- Leu --- --- Trp --- ] D [ --- Ile --- --- Trp --- ] ¼ C [--- Leu --- --- Trp --- ] C [--- Leu --- --- Trp --- ] ¼ (d) What is the real evolutionary importance of such rare events? Explain (3 points) We can generate evolutionary novelty by recombination and without further mutation. Here, we get one extra allele, but if we had three initial mutations, we could have eight different alleles. Such recombinational shuffling of mutations amplifies available variation and genetic combinations considerably beyond the initial mutations themselves.
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PRINCIPLES OF EVOLUTIO N (Fall 2010) ___________ CRIB _____________ Name 2 (2) For a two-allele locus (A 1 and A 2 ), we have three genotypes (A 1 A 1 , A 1 A 2 and A 2 A 2 ), each with its own relative fitness. Describe what will happen with each of the following scenarios, and then plot what happens to average population fitness, as a function of time and the frequency of the A 1 allele ( p 1 ). Use arrows to indicate time trends . (20 points) (a) W 11 > W 12 > W 22 (b) W 11 < W 12 < W 22 W W W W 0 p 1 1 0 p 1 1 p 2 p 2 Tell me what each plot means, in plain English. One allele (or the other) has an unconditional advantage at all allele frequencies, and it
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This note was uploaded on 08/18/2011 for the course ECOLOGY 301 taught by Professor Staff during the Spring '11 term at Rutgers.

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2010Exam-two-Crib - PRINCIPLES OF EVOLUTION(Fall 2010 CRIB Name Second Exam(1 April 2010(1 Imagine a gene coding for some protein The wildtype

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