4.A.3 Cell Specialization Interactions between external stimuli and regulated gene expression result in specialization of cells, tissues and organs.

During the development of an embryo, cells differentiate into specialized cell types that perform specific functions within tissues and organs. Stem Cells Specialized Cells

Genomic Equivalence: Nearly all the cells of an organism have the same genome. Cells differentiate through differential gene expression.

This process is initiated by external and internal cues that trigger regulation of gene expression.

Cell signaling helps direct daughter cells down the appropriate pathways, a process called induction. Cells induce neighboring cells to differentiate. 4 Anterior EMBRYO Posterior Receptor Signal protein daughter cell of 3 Will go on to form muscle and gonads form adult intestine 1 2 3

During induction, signal molecules from embryonic cells cause transcriptional changes in nearby target cells. Early embryo (32 cells) Signal transduction pathway NUCLEUS Signal receptor Signal molecule (inducer)

Structural and functional divergence of cells is due to expression of genes specific to a particular tissue or organ type.

Environmental stimuli can affect gene expression in a mature cell by triggering changes in transcription factors.

Learning Objectives: LO 4.7 The student is able to refine representations to illustrate how interactions between external stimuli and gene expression result in specialization of cells, tissues and organs. [See SP 1.3]