If genetically engineered bees could express a receptor for TNT in their olfactory neurons, how could the transgenic bees be useful for detecting explosives?

Question

A.  Watch for death of the bee when the neuron absorbs TNT.
B.  Use MRI to monitor the brain activity of the bee.
C.  Train bees to respond in a predictable way when the TNT neuron is activated by conditioning them to expect an associated food reward.
D.  Grind up the bee's antennae for use in a TNT ELISA assay.


Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?

Gather Content
What do you already know about olfaction? What other information is related to the question?

Choose Answer
Given what you now know, what information is most likely to produce the correct answer?

Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  Train bees to respond in a predictable way when the TNT neuron is activated by conditioning them to expect an associated food reward.

Clarify Question
What is the key concept addressed by the question?
        · How could transgenic bees help find TDT?
What type of thinking is required?
            o This is an analyze question because you have to break sensory (olfaction) signaling into different stages and understand what activates the receptors involved and how this effects honeybee behavior in order to apply this knowledge to solving a practical problem of TDT detection.

Gather Content
What do you already know about olfaction? What other information is related to the question?
        · You already know that olfaction detects odorants when odorants bind to specific olfactory receptors and opening up ion channels, producing receptor potentials. What would happen if you express a novel olfactory receptor for TDT on honeybee antennae? The honeybee would be able to sense or smell the TDT since TDT, which is a chemical, binds to the receptor on an olfactory neuron. How the bee responds to this stimulus would depend upon which olfactory neuron the receptors are on. If the receptor is co-expressed with other receptors that bind to floral chemicals signaling flowers and a source of pollen, then TDT would attract the bees. Even if the receptor was expressed on olfactory neurons that did not signal pollen, if the two odorants are presented simultaneously (both TDT and floral chemicals), the bee will become conditioned to expect a food reward whenever it smells TDT. Such conditioned bees would be attracted the smell of TDT and could potentially help people detect explosives.

Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
        · Since the TDT receptor that you have genetically engineered in the honeybee antennae is an olfactory receptor, and TDT is a chemical that binds to and activates the receptor, honeybees could be attracted to TDT if they were conditioned to expect a food reward in conjunction with a TDT signal. In fact, the military is currently trying to do just this. The other answers do not seem like very reasonable means of detecting explosives. One answer suggests to watch the death of the bee when the neuron absorbs TNT. First of all, a dead bee cannot provide you with direction- all you would know if that TNT is somewhere nearby. Secondly, although TNT is toxic to animals, it is probably toxic at concentrations that are much higher than detection levels, and it is unlikely that TNT, once bound to the receptor, would then be absorbed into the olfactory neuron. Answer B suggests using an MRI to monitor brain activity of a bee. Although microMRImachines exist, it is highly unlikely that the activity of a few olfactory neurons would be detectable using the resolution available for functional MRI. Also, this technology would be highly expensive and immobile. One answer suggests using a TNT ELISA assay, which seems like a good idea but it is unclear that TDT stays bound to its receptor permanently or whether it only stays for a short moment. In either case, the amount of TDT on the antennae would be miniscule and probably be undetectable by ELISA, which is usually used to detect proteins.

Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o Answering this question correctly depended not only on understanding the steps of the sensory pathway of olfaction, but on your ability to discriminate among different potential means of detecting TDT using honeybees. If you got an incorrect answer, were you unaware of some of the limitations to the techniques proposed in the answers? Did you think that because TDT does not normally have an olfactory receptor in honeybees that binding this receptor would elicit no behaviors, and that bees would be untrainable?