The basic model of quantitative genetics makes what assumpti

That traits are affected by many genes of similar effect and that the observed phenotype of a trait is the sum of genetic environmental effects. b. That traits are affected by many genes of similar effect and that the observed phenotype of a trail is the product of genetic and environment effects. c. That traits are affected by a single gene and that the observed phenotype of a trait is the sum of genetic and environmental effects. d. That traits are affected by a single gene and that the observed phenotype of a trait is the product of genetic and environmental effects. Barnacles are sessile (live attached hard marine crustaceans that live at the edge of the ocean, often where there are heavy waves. During sexual reproduction, the to a transfers a packet of sperm to the female using a more or less elongated penis. Barnacle males face a trade-off between reaching more mates and are conducting, their penises in turbulent water. In a study you are conducting. You find that on exposed shores with heavy wave action, barnacle penises are shorter, but on protected shores with smaller waves, their penises are longer (data shown in figure on the left). You devise an experiment to determine if this variation in barnacle penis length is due to heritable differences among populations or has a purely environmental basis. In this experiment you newly hatched larvae from parents at each site and grow them in the opposite habitat. Larvae from exposed shores are grown in protected shores and vice versa. You allow them to grow up and measure penis length. You data is shown in the figure below.

Solution

The answer is a) That traits are affected by many genes of similar effect and that the observed phenotype of a trait is the sum of genetic and environmental effects.

Quantitative traits are influenced by genetics and by the environment. Under some circumstances, we can partition the phenotypic variance in quanititative traits into variance that is associated with genetic effects, and variance that is associated with environmental effects:

where Vp is the total phenotypic variance, VG is the genetic variance and VE is the environmental variance.