Question

Male guppies with a large tail area are more attractive to female guppies because it provides more surface area for colored spots. A pet shop breeder wants to breed the guppies to increase the male tail area. The current store population has an average tail area of 4.5 mm2, but she only breeds adult guppies with an average tail area of 5.4 mm2 Use this information and the graph below to answer the following questions: a) What will be the average tail area of the offspring in the next generation? b)What fraction of the phenotypic variation in tail area is due to genetic variation? 6.5 5s 45 3.5 Stope 0.54 25 2 Midparent tail area Midoffspring t N

Answer 1

The slope of the given graph i.e 0.54 is actually the heritability of the trait i.e. tail area.

a. The average tail area of the offspring would be the population average (4.5) plus the product of the heritability (0.54) and the selection differential i.e. difference of means of the selected parents (5.4) and the whole population (4.5).

Hence, the average tail area would be 4.5 + 0.54(5.4-4.5) = 4.986 mm²

b. By definition, heritability is the fraction of phenotypic variation due to genetic variation. Hence, 0.54 or 54% of the phenotypic variation in tail area will be due to genetic variation.