Development of Animal Embryos How is development organized in animals?

What determines how different segments of an organisms will develop?

Differentiation Stem cells--> Programmed cells –Homeotic Genes or Hox genes: transcription factors develop specific tissue programming. Think about it? What happens when the homeotic genes are not activated? Activated in the wrong set of cells?

Hox Mutations

Cloning: Nuclear Transplantation Is the nucleus the only important developmental determinant? What other factors/information is necessary?

Why can ’ t we program stem cells?

How do cells know what to be? Induction Paracrine signalling *Induction can work in reverse. Why are iPS stem cells so useful?

Pattern formation evolutionarily conserved

Basic Stages of Development

Cleavage p Similar to segmentation in frogs. Model Organism: Sea urchins; amphibians –Animal pole: head –Vegetal pole: yolk

Blastocyst-->Gastrula Blastopore can become mouth or anus depending on organism: –Protosome: blastopore, mouth –Deuterosome: blastopore, anus What organism is the sea urchin?

Protosomes and Deuterostomes: Unity and Diversity

Gastrulation: Forms Tissue Layers 3 Tissue layers; lead to organogenesis –“ tripoblastic ”

Find and Memorize: Ectoderm forms… Endoderm forms… Mesoderm forms…

After Gastrulation  Neurulation –Formation of central nervous system (ectoderm) and notocord (mesoderm)

Down the road…what is an egg? –Who has this type of egg?

What must you do? Be able to look at various embryo slides and identify stages and vocabulary. Stages: early cleavage, late cleavage, blastula, gastrula Vocabulary: blastopore, animal pole, vegetal pole, grey crescent, notocord, endoderm, ectoderm, mesoderm Use the pictures in your book to analyze what you see.