BICD 100 Final 2005

BICD 100 Final 2005 - Name PID BICD100 Final Exam 1 In a...

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1 Name _______________________________________ PID _____________________ BICD100 Final Exam 3/17/05 1.) In a field of transgenic corn expressing a certain Bacillus thuringiensis toxin, European Corn Borers are killed unless they have become resistant to the toxin. When resistance alleles arise, they are rapidly amplified by selection. You are a population geneticist making recommendations to the EPA regarding the effectiveness of planting an area of non transgenic corn around B.t. corn fields (a so-called “non B.t. corn refuge”) as a strategy for slowing the growth of the resistant insect population. In a particular test field, a new dominant resistance allele arose in the European corn borer (call it R). Shortly afterwards, sampling of the population showed that 2% of the insects were resistant to B.t. (assume that all of these were heterozygous Rr) and the remaining 98% were B.t. sensitive (rr). a. At the time this sample was taken, what was the frequency of R alleles?__ _____ __[call this p = f(A)] (4 pts) r alleles?__ ____ ___[call this q = f(a)] b. If this were a non B.t. cornfield so there was no selection for resistant insects, what would be the frequency of resistant insects in the next generation? (Assume that mating is random, there is no migration in or out of this population, and no new resistance alleles arising through mutation – 6 pts). c. In the B.t. cornfield where all sensitive insects die before reproducing, what will be the new frequency of resistant insects after one generation (assume mating is random and no new R alleles arise through mutation – 10 pts)? d. If no new insects migrated into the B.t. cornfield, what would be the frequency of resistant insects after another round of reproduction (as before, assume mating is random and no new R alleles arise through mutation – 8 pts)? e. Due to the presence of a non B.t. corn refuge around the field, the population in c (that is, the population as it stands after one generation of selection) is actually joined by an equal number of B.t. sensitive immigrants before reproducing again. What will be the actual frequency of resistant insects in the next generation? (12 pts)
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2 2.) Time to flowering is an agronomically important trait in corn, as for other crop plants. In Northern climates with short growing seasons, a short time to flowering is a useful trait. To identify genetic factors controlling time to flowering in corn, a corn geneticist crossed Gaspay Flint (an inbred line with a very short time to flowering of 35 days) to another inbred line called N28 (with a long time to flowering of 52 days). In the F 1 hybrids, time to flowering was 43 days (standard deviation 3 days). F 1 s were crossed together to produce an F 2 generation whose mean time to flowering was 44 days (standard deviation 8 days). a. What value for broad sense heritability of time to flowering in corn is indicated by this data? (10 pts) F 2 progeny were scored individually for time to flowering and also analyzed to determine their genotypes for molecular marker loci distributed throughout the genome. In the graph below, r values are plotted on
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