The early stages of embryonic development determine the pattern of structures in the adult organism
The study of Drosophila mutants with disrupted development patterns has identified genes that control development
The generation of a body pattern depends on the positional information that each cell receives during development
The gene products of maternal effect genes are deposited asymmetrically into the oocyte and establish the anteroposterior and dorsoventral axes at a very early stage of development
Gap, pair-rule, and segment-polarity genes act sequentially to divide the Drosophila embryo into segments
The expression of homeotic genes controls the phenotypic characteristics of segments
The developmental fate of each cell in the nematode Caenorhabditis elegans is known
Heterochronic mutations disrupt the timing of developmental changes in C. elegans
Vertebrate Development
Researchers have identified homeotic genes in vertebrates
Genes that encode transcription factors also play a key role in cell differentiation
Plant Development
Plant growth occurs from meristems that are formed during embryonic development
Plant homeotic genes control flower development
Sex Determination in Animals and Plants
In Drosophila, sex determination involves a regulatory cascade that includes alternative splicing
In C. elegans the ratio of X chromosomes to autosomes initiates a regulatory cascade that determines sex
In mammals, the Sry gene on the Y chromosome determines maleness
In sexually dimorphic plants, the male plant is usually heteromorphic
