Types of genes

Recently, research into embryonic development has given us an even better insight [blank] how major structural changes might occur in a given population of organisms. We now understand that there are two major types of genes: developmental and "housekeeping" genes. Developmental genes are those that are expressed during embryonic development, and their proteins [blank] the symmetry, skeletal development, organ placement, and the overall form of the developing animal. [blank] , "housekeeping" genes are expressed during the animal's daily life to generate proteins that keep the cells, tissues, and organs in the body functioning properly. as you might suspect, mutations in developmental genes can have radical consequences for body form and function, whereas mutations in "housekeeping" genes tend to [blank] the health and reproductive success of the post-embryonic animal.