Cell Communication & Cycle unit test
A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.
Second messenger
Cancer as checkpoint failure
Meiosis I vs meiosis II
Receptor specificity
Calcium as a second messenger
Centrosome and spindle
Sister chromatids vs homologous chromosomes
Meiosis vs mitosis
cAMP pathway
Apoptosis
Signal termination
Cytokinesis
Short answer 1. Define or explain: Synapsis and tetrads
3 ptsShort answer 2. Define or explain: G1 checkpoint
3 ptsShort answer 3. Define or explain: Negative and positive feedback
3 ptsShort answer 4. Define or explain: Lab: Mitosis and Meiosis
3 ptsFree response
9 ptsMany insects rely on pheromones released by females to find mating partners. Scientists hypothesize that in a certain moth, the behavior of male moths in response to pheromones is regulated by the extracellular signaling molecule 20E. To test whether the binding of 20E to its receptor DopEcR affects behavior, scientists injected male moths with saline (control) or with siRNAs that inhibit expression of the gene encoding DopEcR. They exposed the moths to the pheromone and recorded the percent of total observed time spent in general activity (movement in any direction), and the percent of that general activity time spent in oriented activity (movement toward an area of high pheromone concentration). TABLE 1. AVERAGE GENERAL AND ORIENTED ACTIVITY IN MALE MOTHS (± 2SE of the mean) Treatment General activity Oriented activity (% of total time) (% of general activity) Injected with saline (control solution) 95 ± 5 60 ± 4 Injected with siRNAs inhibiting DopEcR 90 ± 8 25 ± 6 FIGURE 1. A simplified model of the signaling pathway. 20E binds DopEcR, a G protein-coupled receptor spanning the plasma membrane. Before binding, the associated G protein is inactive with GDP bound to its Gα subunit. When 20E binds the receptor, GTP displaces the GDP on Gα, the G protein becomes active, and the activated pathway leads to increased expression of genes associated with oriented activity in male moths.
(a) Many receptors are embedded in the plasma membrane. Describe the polarity of the portion of the receptor that is inside the membrane.
(b)(i) The released exam supplies a grid. State what type of graph represents the data in Table 1 appropriately, and why.
(b)(ii) State what belongs on each axis, including units, and what the error bars represent.
(b)(iii) State how the two activity measures should be arranged for each treatment, and confirm an error bar is plotted on every mean.
(b)(iv) Based on the data in Table 1, determine the type of activity that was affected by inhibiting the expression of the DopEcR receptor.
(c)(i) Based on Table 1, identify the treatment group in which the oriented activity was greater than 50% of the general activity.
(c)(ii) The scientists studied some moths with a mutation in the gene encoding the G protein that prevents GTP from displacing the GDP bound to the G protein. Based on Figure 1, predict the effect of this mutation on the oriented activity in male moths exposed to the pheromone.
(d)(i) Expression of the gene encoding DopEcR is low in male moths during their first few days as adults, when they are sexually immature, and rises rapidly as they reach sexual maturity. The scientists claim that this increase in gene expression increases the likelihood of males finding females with whom to mate. Use evidence from the information provided to support the claim.
(d)(ii) Based on Figure 1, explain how an inhibitor of the DopEcR pathway might serve as an effective chemical to protect crops from moth damage.