Old Midterm1Key.a08

Old Midterm1Key.a08 - PLANT BIOLOGY 113 SPRING 2008 NAME...

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PLANT BIOLOGY 113, SPRING 2008 MIDTERM #1 PAGE 1 APRIL 24, 2008 NAME KEY HARD COPY OF ANSWERS DUE BY 5 PM, FRIDAY, APRIL 25 IN THE PLANT BIOLOGY OFFICE, 1002 LS. You can use your notes, handouts, and text only. You are operating under the UC Davis Honor Code - DO NOT CONSULT WITH ANYONE ABOUT THIS EXAM. Please be sure that you have 6 pages. Some of the examples are hypothetical. 300 POINTS TOTAL QUESTION 1 (15 POINTS) : What is a gametophyte? What is a major difference between a gametophyte and a sporophyte? Name the two gametophytes of plants. 1. Gametophytes are haploid organisms that give rise to gametes (5 points). 2. Gametophytes are haploid, whereas sporophytes are diploid (5 points). 3. Male gametophyte or microgametophyte or pollen grain and female gametophyte or megametophyte or embryo sac (5 points). QUESTION 2 (15 POINTS) : List two similarities and two differences between the molecular definition and the genetic definition of a gene. 1. Similarities: a. Both define a gene as an independent unit of DNA. b. Both define a gene as having a function 2. Differences: a. A geneticist defines a gene on the basis of heritability whereas a molecular biologist define a gene as a structural unit. b. The promoter would be included in a genetic definition but not a molecular definition of a gene. Question 3. You are conducting an undergraduate research project characterizing the organization of a newly discovered plant, Selaginella obamaceae . E XPERIMENT A: You prepare a genomic library consisting of 1 kb fragments from S. obamaceae genome. You then pick 100 clones at random, isolate the 1 kb genomic DNA fragments from these clones, label the fragments with radioactivity, and hybridize each fragment individually with a gel blot of nuclear DNA from S. obamaceae . The following results are obtained. HYBRIDIZATION WITH 1 KB GENOMIC DNA FRAGMENTS 60 clones with pattern A 40 clones with pattern B (NOTE: clones generate similar but not identical patterns) QUESTION 3A (20 POINTS) : On the basis of this experiment alone, what fraction of the S. obamaceae genome consists of repeated and single (or low) copy DNA? Explain and qualify your answer. 1. 60% of the clones contain repeated DNA (7.5 points). Sixty percent is the maximum estimate of the percentage of repeated DNA in the genome, because clones containing both single (low) copy and repeated DNA will yield hybridization pattern A (2.5 points). 2. 40% of the clones contain only single copy DNA (7.5 points). Forty percent is a minimum estimate of the single copy DNA in this plant (2.5 points). 3. Assumes randomly-picked genomic clones are representative of the genome.
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PLANT BIOLOGY 113, SPRING 2008 MIDTERM #1 PAGE 2 APRIL 24, 2008 NAME KEY E XPERIMENT B: Next, you prepare a genomic library that consists of 20 kb fragments of the S. obamaceae genome. You pick 100 clones at random, label the cloned DNA with radioactivity, and hybridize each fragment individually with a gel blot of S. obamaceae genomic DNA. The following results are obtained.
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Old Midterm1Key.a08 - PLANT BIOLOGY 113 SPRING 2008 NAME...

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