1. Stage 10 Human Embryo (~ 22 Days)

2. Somite Formation from Pre-Somitic Mesoderm

4. Somite Formation and Hairy Gene expression

5. Hairy Gene Expression

6. Homeotic (Hox) Genes
Hox a
Hox b
Hox c
Hox d

7. Hox Gene Expression Along A/P Axis
(Posterior margin of Hox Genes Expression)

9. “Hox Code” Concept

10. Hoxc8 Deletion in Mouse

12. Forelimb Development
in chick and mouse

13. Limb Bud Development

14. Sonichedgehog (Shh) Expression in Limb Bud

15. Ectopic Application of Shh Protein

16. Hox Gene Expression in Limb Bud
Hox a genes
Hox d genes

17. Synpolydactyl Phenotype
Hoxd13 mutation

18. Digit Formation
Programmed Cell Death

19. Programmed
Cell Death
Pathway
(BMP?)