BIO411: Genome Regulation - Cytoplasmic Determinants

Cytoplasmic Determinants and Inductive Signals

• Egg cytoplasm contains RNA, proteins, and other substances distributed unevenly, influencing early development.
• Cytoplasmic determinants are maternal substances in the egg that influence early development.
• As the zygote divides by mitosis, cells contain different cytoplasmic determinants, leading to different gene expression.
• The environment around the cell, especially signals from nearby embryonic cells, provides developmental information.
• Induction: signal molecules from embryonic cells cause transcriptional changes in nearby target cells, inducing differentiation of specialized cell types.

Sequential Regulation of Gene Expression

• Determination commits a cell to its final fate.
• Determination precedes differentiation.
• Cell differentiation is marked by the production of tissue-specific proteins.

Pattern Formation: Setting Up the Body Plan

• Pattern formation is the development of a spatial organization of tissues and organs.
• In animals, pattern formation begins with the establishment of the major axes.
• Positional information provides molecular cues that control pattern formation, telling a cell its location relative to the body axes and neighboring cells.

The Life Cycle of Drosophila

• Cytoplasmic determinants in the unfertilized Drosophila egg determine the axes before fertilization.
• After fertilization, the embryo develops into a segmented larva with three larval stages.