2. A Morphogen is a Developmentally Important Type of Secreted Signal Morphogens have the following characteristics: 1. They are synthesized in some but not all cells. 2. They diffuse from the site of synthesis and are less concentrated the farther away from the source of synthesis. 3. Cells respond to different morphogen concentrations by activating expression of distinct sets of genes.

3. Morphogens

4. How the early frog embryo maps onto the tadpole Organizing Centers Orchestrate Embryonic Development

5. Mangold’s organizer transplantation experiment

6. Organizer grafts induce a second axis

7. A mutant is different than “normal”. The mutant characteristic is passed on to the next generation.

8. DNA Central Dogma of Biology DNA -> RNA -> Protein mRNA Transcription Translation Protein Gene Function

9. Abnormal Gene Function DNA mRNA Transcription Translation Protein DNA -> RNA -> Protein Synthesis of Abnormal Proteins Mutations Often Result in the X X X

10. Recessive versus Dominant Mutations Recessive mutations: Both copies of the gene must be mutated to manifest defect. Dominant mutations: The defect is manifest when only copy of the gene is mutated Loss-of-function mutations are typically recessive Recessive mutations are represented by lower case letters + = wildtype, m = recessive mutation Dominant mutations can confer new activities or interfere with normal gene function Dominant mutations are represented by upper case letters + = wildtype, M = dominant mutation

11. Genotype versus Phenotype Genotype: The genetic make-up of an individual Phenotype: The appearance of an individual Examples: +/+, +/m, m/m, +/M Example: Individuals having a +/+ or +/m genotype have a normal phenotype. Individuals having m/m genotype have mutant phenotype. Individuals with one normal (+) and one mutant (m) copy of a gene are called carriers for the mutation (+/m).

12. Abe Lincoln

13. mf/mf = 1/4 offspring = Marfan +/+ = 1/4 offspring = Normal or+/mf mf/+= 1/2 offspring = Normal ++ mf + + One quarter of the offspring from two Marfan carrier parents will have Marfan Syndrome + mf Two types of mother’s eggs + mf Two types of father’s sperm +/mf +/+ mf/+ mf/mf

14. Mutation of the Fly dpp gene