Essay #1 February 25 – February 29 due Thursday February 28
(Hint: Refer to Lab Bench Lab #
6 Molecular Biology) Most cells of the bacterium Escherichia coli are able to grow on a relatively simple minimal medium containing
glucose, vitamin B1, and mineral salts. However, many mutants of E. coli are unable to synthesize particular substances and can grow
only if these substances are added to the medium. In E. coli, strains 1 and 2 are of opposite mating types.
The following table records
the results of streaking two strains separately on the following media:
Strain 1
Medium A (minimal) - Growth
Medium B (minimal
+ Streptomycin) - No Growth
Medium C (minimal + Streptomycin + Leucine + Threonine) - No Growth
Medium D (minimal minus Vitamin B1)
- No Growth
Strain 2
Medium A (minimal) - No Growth
Medium B (minimal + Streptomycin) - No Growth
Medium C (minimal + Streptomycin
+ Leucine + Threonine) - Growth
Medium D (minimal minus Vitamin B1) - No Growth
However, if strain 1 is mixed with strain
2 and then streaked across a plate of medium B, colonies will develop. If many plates of medium D are streaked with strain 1, an occasional
colony of E. coli is found. On the basis if the experimental information obtained from the data, answer all of the following:
a) Develop
hypotheses to explain the results in the table.
b) Develop a hypothesis to explain the results obtained when the two strains are mixed
and then streaked on medium B.
c) Develop a hypothesis to explain the occasional colonies growing on medium D and design an experiment
to test your hypothesis.
d) In a molecular biology laboratory, a student obtained competent E. coli cells and used a common
transformation procedure to induce the uptake of plasmid DNA with a gene for resistance to the antibiotic kanamycin. If a student
wants to verify that transformation has occurred, what procedure should she use? How should she set up the experiment?
Essay
#2 March 3 – March 7 due Thursday March 6
The making of the various types of protein is one of the most important events for a cell
because protein forms structural components of the cell and composes the enzymes that catalyze the production of the remaining organic
biomolecules necessary for life. The genotype coded for in the DNA is expressed as a phenotype by the protein and other enzyme-catalyze
products.
a) Describe protein synthesis in terms of the molecular structure of the nucleic acids.
b) Using a specific example, explain
how a new phenotypic characteristic may result from a change in DNA
Essay #3 March 10 – March 14 due Thursday March 13
Describe the pancreas in terms of: a) position or location, b) cell type, c) duct system, d) exocrine secretions, e) diabetes mellitus
relationships
