1. AP Biology Development

2. AP Biology Big Questions: 1. How does a multicellular organism develop from a zygote? 2. How is the position of the parts of an organism determined? 3. How does differentiation of cell type occur in organisms? 4. How are genetics and development connected? Environment?

3. AP Biology Development is Regulated  The development of an organism is coordinated by sequential changes in gene expression.  Multicellular organisms must regulate:  Cell division  Differentiation  Morphogenesis

4. AP Biology Early Developmental Pathways  Cytoplasmic Determinants  unequal distribution of mRNA and proteins from mother  Embryonic Induction:  Local signaling by nearby cells send cells down a specific developmental path.

5. AP Biology

6. Pattern Formation  Cells need to establish their position in the developing organism. (head/tail, right /left etc.)  Cytoplasmic determinants and induction lead to gradient morphogens.

7. AP Biology Cellular Differentiation  Germ lines established  Cell type already determined  Differentiation accomplished by the expression of cell type- specific proteins.  There is normally no turning back.

8. AP Biology Differentiation Control  Genes must be both turned on and turned off at appropriate times and locations.  Regulated by internal and external cues

9. AP Biology Internal Cues  DNA packing, micro RNA’s and epigenetics can switch genes ON or OFF.  Transcription factors must be present and can be either stimulatory or inhibitory.

10. AP Biology External Cues (outside the cell)  External cues signal to cells, causing cells to alter their gene expression.

11. AP Biology Environmental Cues  The presence of particular molecules and conditions in the local environment is required for development to proceed properly.  Ex. The role of temperature and moisture in seed development. Why do you water a seed after you plant it? Hmm…

12. AP Biology Environmental Cues  Changing the environment around the cells can alter gene expression.

13. AP Biology Apoptosis  “Programmed cell death”: Important role in defining borders and openings in the developing organism.

14. AP Biology Homeobox (HOX) Genes  A family of related genes that serve as master regulators of animal development in all animals on the planet.

15. AP Biology Experimental Evidence  Mutations in normal developmental pathways lead to malformations in embryonic development

16. AP Biology Experimental Evidence  Transplantation Experiments: Moving regions of a developing embryo affects normal pattern formation.