The arctic fox is brownish-grey in summer and white in winter. From your knowled

Question

The arctic fox is brownish-grey in summer and white in winter. From your knowledge about coat colour in Siamese cats, answer the following questions about the arctic fox: Come up with a logical hypothesis to explain the seasonal coat colour changes for the arctic fox (focus on the function of the enzyme(s) involved). Outline a simple and humane experiment to test your hypothesis. What other adaptation in the fox allows for rapid coat colour change in the spring when the fox changes from white to greyish-brown?

Explanation / Answer

a). During winter, decreased Sun light causes supression of genes coding for melanocyte stimulating hormone (MSH), and decreased number of MSH receptors that stimulates the growth of white fur during winter. Whereas in summer, gene expression predominantes resulting in brown colour.

(b) The extent of gene expression can be tested in the presence and absence of Sun light.

(c) During summer, the skin coat becomes thinner, which is thick during winter. Its body surface area to volume ratio is also small. Its countercurrent heat exchange mechanism provides very good insulation.

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