4.A.3 Cell Specialization

Interactions between external stimuli and regulated gene expression result in

specialization of cells, tissuesand 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

ReceptorSignalprotein

Signal

Anteriordaughtercell of 3

Posteriordaughtercell of 3

Will go on toform muscle and gonads

Will go on toform adultintestine

12

43

3

During induction, signal molecules from embryonic cells cause transcriptional changes in nearby target cells.

Early embryo(32 cells)

NUCLEUSSignaltransductionpathway

Signalreceptor

Signalmolecule(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]