- Stem Cells: unspecialized cells during early stage of embryonic development that can reproduce indefinitely and differentiate (become any) into specialized cells
- But as development continues → cells differentiate & become specialized → cell divisions make more specialized cells
- Cells become specialized because transcription factors activate some genes while suppressing others
- Process is self-reinforcing as the cell can signal to itself
- Genes permanently turned off associated with DNA methylation and histone modification
- Embryonic stem cells (ES): Can become any kind of cell (including sperm and egg)
- Adult body stem cells: can only replace non-reproducing specialized cells (not sperm and egg)
- Pluripotent: can become any type of cell
- Totipotent: cells that can form new fetus
- Unipotent: a cell that has differentiated and cannot become any type of new cell
- Differential Gene Expression: expression of different genes by cells with the same genome
Morphogenesis, Pattern Formation, and Axis Development
- Pattern Formation: the process of organizing tissues and organs that begins in early embryo
- Various genes code for pattern formation of organisms
- Positional Information: molecular cues that control pattern formation, tells a cell its location relative to the body’s axes and to other cells
- Maternal effect: offsprings axes encoded by mother’s genes (ie. Cytoplasmic determinants),
So mutations passed to all