Question 3. Intertidal mussels, Mvtilus txossulus, collected from the same site

Question

Question 3. Intertidal mussels, Mvtilus txossulus, collected from the same site in Washington, USA, in February and August were exposed for 2 h to different temperatures in the lab Dissected gill tissue was then metabolically labeled at 13°C in the presence of 35S-labelled met ions/cysteine before proteins were separated on 10 % SDS-polyacrylamide gels and imaged using standard fluorographic techniques. Individual lanes were loaded with equal counts of radioactivity (3.7'107 Ba), and the locations of molecular mass markers (not shown) areindicated on the right. Visible bands are indicative of protein expression; the darker the band, the more protein expressed. Heat-shock temperature (°C) 20 23 25 28 200 kDa 90 kDa 70 kDa 40 kDa AY), February August A. What is/are the independent and dependent variable(s) in this study? B. In response to thermal stress, many organisms increase their production of heat shock proteins, including Hsp70, a 70 kDa molecular chaperone that functions to stabilize other proteins. What do the above results tell us about the relative stress experienced by mussels in the different treatment groups? C. Based on these results, when are mussels from this location most physiologically resistant to high temperature stress? When are they most likely to experience high temperature stress? D. Given that mussels can live for 10+ years, what is the likely biological mechanism underlying these results (i.e., this would be an example of what phenomenon)?

Explanation / Answer

A. Independent variables are the experimental conditions that are being subjected to the experimental model. Dependent variable is the outcome or characteristics of the model that is being measured.

Here, independent variable is varying temperature and dependent variable is the amount of protein expression.

B. In response to the heat stress, mussels activates the expression of HSP (heat shock protein) and chaperons. The onset of HSP chaperons vary in experimental groups. In february, HSP activated on 23 degree celsius, but during august, it activated on 28 degree celsius. It means the initial temperature did not pose any stress on the mussels during both the seasons. But, the amount of proteasome subunits were more in august experimental setup; comparatively high on 28 degree exposure. High temperature exposure during august poses relatively more physiological stress.

C. Mussels from this location is most physiological resistant to high temperature stress during february, and during august, they are most likely to experience high temperature stress.

D. High temperature stress during hot seasons are coped up by increased expression of HSP proteins. They are most likely to Acclimatize to the environmental condition by altering the quantity and quality of gene expression.

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