Chapter 5 Answers

    1. Mutagenize a wild type (auxotrophic) strain and screen for mutations that fail to grow on minimal media, but grow well on minimal media supplemented with proline.
    2. Take mutants #1-#10 and characterize them, based on:
      1. genetic mapping of the mutants (different locations indicate different genes);
      2. different response to proline precursors (a different response suggests different genes);
      3. complementation tests among the mutations (if they complement then they are mutations in different genes).
    3. If the mutations are in different genes, the F1 progeny would be wild type (able to grow on minimal medium without proline).
    4. If the mutations are in the same gene, the F1 progeny would NOT be wild type (unable to grow on minimal medium without proline).
  1. There are many correct answers for this question. Here is one:
    1 2 3 4 5 Mutant in Loci
    1 Mutant in locus (1,2)
    2 Mutant in locus (1,2)
    3 + + Mutant in locus (3)
    4 + + + Mutant in locus (4)
    5 + + Mutant in locus (3 and 4)
  2. The auxotrophic strain is mutant in one gene. This gene has both a HindIII and XhoI site within its sequence, but not an EcoRI Thus, the EcoRI library could contain a restriction fragment with an entire, intact gene, while the two other enzymes would break the gene into two fragments that would not be cloned together as a functional gene.
  3. E. coli cells do not normally import proteins from their environments, thus none of the Enzyme A proteins would enter the cells to affect a rescue. If the product of Enzyme A was added, then it could rescue the strain, but only if the product could be taken up by the cells.

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Open Genetics by Natasha Ramroop Singh, Thompson Rivers University is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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