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 55 45 3.5 Stope 0.54 25 2 Midparent tail area Midoffspring tail are

Answer 1

a) To find the area of the tail of the next generation we can consider the following :

The slope of the given graph represent

= Difference between two values of average tail area of offspring/Difference between two values of average tail area of adult

= (y₂-y₁) / (x₂-x₁)

If the adult population has an average tail area of 4.5, then it can be taken to be x₁ and the offspring produced with the tail area of 5.4 can considered to be y₁.

Now for the next generation the adult of this generation has the same tail area as the offspring of the previous generation.

So x₂ is 5.4 and we have to find the tail area of offspring of this generation,i.e., y₂.

As the slope=0.54 = (y₂-y₁)/(x₂-x₁)  = (y₂-5.4)/(5.4-4.5)

0.54= (y₂-5.4) / 0.9

0.54 * 0.9 = y₂-5.4

0.486= y₂-5.4

So, y₂ = 0.486 + 5.4 = 5.886

Thus the required tail area of the offspring of next generation is 5.886 mm².

b) Heritability = Slope = 0.54 = Genetic variation/ Phenotypic variation

It (Heritability) is defined as the fraction of phenotypic variation due to genetic variation that is the required value.  

So the required fraction is 54/100 = 27/50.