Sample exam integration problem
In the late 1960s, a vibrant new research field was ignited by the discovery that instead of fixing CO2 into
a C3 compound, some plants initially fix CO2 into a four-carbon (C4) compound. A diagram depicting the
two photosynthetic pathways is shown below:
QUES 1- 3: Consider the evolution of the C4 pathway by natural selection within a particular plant
species. Which of the following statements would be true?
1. Mutations that generated alleles for the C4 pathway occurred due to exposure to a hot, dry climate.
a. True
b. False
2. In order for the pathway to evolve in a population, individuals with C4 related alleles produced more
viable, fertile offspring than individuals without these alleles.
a. True
b. False
3. Assuming a large population, if C 4 related alleles increased the fitness of individual plants in their
environment, the frequency of the alleles would increase in the population over time.
a. True
b. False
QUES 4-7: Identify whether the statements below apply to C3 plants, C4 plants, or both C3 and C4.
4. The gene encoding the Rubisco protein would be present in the mesophyll cell.
a. C3 plants only
b. C4 plants only
c. Both C3 and C4 plants
5. The Rubisco protein would be present in the mesophyll cell.
a. C3 plants only
b. C4 plants only
c. Both C3 and C4 plants
6. The transcription factors required for production of the Rubisco mRNA would be found in the
mesophyll cell.
a. C3 plants only
b. C4 plants only
c. Both C3 and C4 plants
7. The 3-carbon sugar glyceraldehyde-3-phosphate (G3P) is a final product of photosynthesis in the plant.
a. C3 plants only
b. C4 plants only
c. Both C3 and C4 plants
8. The active site of the Rubisco enzyme has a binding site
for both CO2 and RuBP. The active site for Rubisco is
modeled in the diagram at right. Note that the amino acids
ARG2 and LYS5 are positioned so that ionic bonds can be
made with the phosphate groups of RuBP.
If the amino acid LYS5 (+charge) were mutated to a
non-polar VAL, what would likely happen to the amount
of activation energy required for Rubisco to catalyze the
addition of CO2 to RuBP?
a. The amount of activation energy required would not
change.
b. The amount of activation energy required would
increase.
c.The amount of activation energy required would decrease.
QUES 9-11. The segment of Rubisco mRNA below codes for amino acids that make up the active site.
The codon for one amino acid, lysine is shown in bold below.
…. AUG CCC GGC AAA GUU GCC CGG
…
There are a number of described mutations that involve the
active site of Rubisco.
For the mutations to the Rubisco gene shown below, RANK the
mutations from MOST DELETERIOUS, INTERMEDIATE,
and NO EFFECT. Use each choice only once.
9.
…
…. AUG CCC GGC AAU GUU GCC CGG
a. Most deleterious
b. Intermediate
c. No effect
10.
…. AUG CCC GGC AAG GUU GCC CGG
a. Most deleterious
b. Intermediate
c. No effect
…
11.
…. AUG CCC GG AAA GUU GCC CGG
C DELETED
a. Most deleterious
b. Intermediate
c. No effect
…
^