Master Regulatory Genes That Turn on Entire Programs of Development

Multiple Choice

Master regulatory genes that turn on entire programs of development are often identified because loss-of-function mutations and gain-of-function mutations in the gene have opposite phenotypes. Which type of mutation is recessive? Which type of mutation is dominant?

A) Loss-of-function mutations and gain-of-function mutations are recessive.
B) Loss-of-function mutations are recessive; gain-of-function mutations are dominant.
C) Loss-of-function mutations are dominant; gain-of-function mutations are recessive.
D) Loss-of-function mutations and gain-of-function mutations are dominant.
E) There is no predictable pattern of recessiveness or dominance.