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question 61

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Use the following information to answer the question.
The mechanism of cell crawling in protist species is not well defined. Pseudopodia extension involves interactions between actin and myosin (the same molecules that are involved in vertebrate muscle contraction) . However, prior to the study described below, no one had provided convincing data that actin and myosin were actually involved in cell crawling in protists. Anatomical studies had identified the cytoskeletal protein actin just below the surface of the cell membrane in several species of protist, but physiological studies had failed to show a functional link between actin, myosin, and cell crawling.
In a study by N. Poulsen et al. (Diatom gliding is the result of an actin-myosin motility system, Cell Motility and the Cytoskeleton 44 (1999) :23-22) , researchers tested whether motility in a particular species of diatom involves interactions between actin and myosin.

Refer to the study by Poulsen et al. and the figure above. Cultures of a species of diatom were treated with BDM, a reversible inhibitor of myosin function. Which of the following predictions is consistent with the hypothesis that an actin-myosin interaction is necessary for motility?

Definitions:

Reinforcement

Any event or stimulus that, when following a response, increases the probability that the response will occur again.

Token Economy

A system of behavior modification based on the systematic reinforcement of target behavior, where tokens that can be exchanged for various rewards are used as reinforcers.

Extinction

In psychology, the gradual weakening and disappearance of a conditioned response when the conditioned stimulus is repeatedly presented without the unconditioned stimulus.

Obsessive-Compulsive Behaviors

Patterns of behavior characterized by intrusive thoughts (obsessions) and repetitive behaviors or mental acts (compulsions) performed in response.