Use the Following Information to Answer the Question(s) Below

question 30

Multiple Choice

Use the following information to answer the question(s) below.
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 accompanying figure. The data graphed in the figure could be an artifact if latrunculin A kills this species of diatoms (that is, that may be why the cells are not moving) . Which of the following would be the best evidence that latrunculin A is NOT killing the cells?

• A) When the toxin was washed off the culture, the cells began to move again.
• B) There were still a small percentage of motile cells in the culture treated with the toxin.
• C) Most of the cells in the control were moving, indicating that they were alive.
• D) When the toxin was applied to another species of diatom, 25 percent of them continued to move.

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Definitions:

Body Fat

A component of the body that consists of stored fat and is essential for normal physiological and metabolic functions.

Correlation

An indicator that measures the degree to which multiple variables vary in unison.

Denseness

A measure of the compactness or crowding of objects within a given area or volume.

Slope

The measure of the steepness or inclination of a line, often describing the rate of change between two variables.