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EXPERIMENTAL DESIGN

The Hardy-Weinberg equilibrium

There are some concepts in biology that are best learned and understood by problem-solving. One such concept is the Hardy-Weinberg equilibrium, which states that allele and genotype frequencies within a population will remain constant from generation to generation unless some external influences act directly on those alleles or genotypes. Here, geneticist Kevin O’Dell takes you on an imaginary journey to the fictitious Scottish Island of Eilean nan Caorach Geala (White Sheep Island)

One of the most successful Scottish businesses of recent years is Eilean nan Caorach Geala Farm. The farm occupies the whole of Eilean nan Caorach Geala (see Figure 1), a small, fictitious 25km2 island in the Outer Hebrides, off the coast of northwest Scotland. The owners and brains behind the enterprise are Farmer Collogie, a former genetics graduate, and his partner Simon, an animal behaviour expert who prefers to be called Si. It is this unique combination of genetic and animal behaviour skills of Farmer Collogie and Si that appears to have given Eilean nan Caorach Geala Farm the edge over all of their competitors. Understandably they are very proud of their unique stock of pure-bred Caorach Geala sheep, which are the only sheep on the island.

The success of Eilean nan Caorach Geala Farm was severely compromised when, early in 2010, the whole of western Scotland was struck by the ‘storm of the century’. Caught up in the carnage of storm Elizabeth was the French ship The Auld Alliance and its cargo of around a hundred pure-bred Mouton Blanc (French White sheep). Unfortunately, in the chaos of storm Elizabeth, nobody noticed that the wreck of The Auld Alliance reached Eilean nan Caorach Geala, potentially depositing panicstricken French sheep onto the island.

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Vaccine hesitancy and the global resurgence of measles

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Cetaceans: masters of the ocean or out of their depth?

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