Two of the Genes That Affect Coat Colour in Horses

Multiple Choice

Two of the genes that affect coat colour in horses are the extension gene and the cream dilution gene. The dominant E allele at the extension gene generates black coats, while the recessive e allele produces red coats. The coat colour caused by the extension gene is not altered if the horse is a homozygote for the C allele at the cream dilution gene. However, if the horse is a homozygote for the C^Cr allele at the cream dilution gene, it will have a white coat regardless of the extension genotype. This interaction between the extension and the cream dilution gene is an example of

A) pleiotropy.
B) epistasis.
C) codominance.
D) random assortment.