1. Chapters 47 & 21 Animal Development & The Genetic Basis of Development

2. DEVELOPMENT An organism arises from a fertilized egg as the result of three related processes – Cell division – Cell differentiation – Morphogenesis

3. How does the ball of cells know when and where to differentiate, fold etc.? Cytoplasmic Determinants ! (usually maternal factors like mRNA, proteins, other chemicals) They are non-homogenous

4. Early Morphogenesis: Gastrulation & Neurulation Neurulation video http://www.yo utube.com/wa tch?v=ZeIyrInO nMc http://www.yo utube.com/wa tch?v=ZeIyrInO nMc

5. Fertilization Gray crescent Establishing the body axes What is determination? What is induction?

6. REGULATION OF GENE EXPRESSION Transcriptional regulation is directed by: TRANSCRIPTION FACTORS such as: – Maternal molecules in the cell’s cytoplasm (cytoplasmic determinants) – Signals from other cells (induction)

7. Drosophila melanogaster Each segment in the adult fly is anatomically distinct – And also has characteristic appendages… just like you? HEAD THORAX ABDOMEN

8. Drosophila melanogaster Maternal cytoplasmic determinants – GRADIENTS of chemicals are important Segmentation genes – Gap genes – Pair rule genes – Segment polarity genes – http://www.youtube.com/watch?feature=endscreen&v=MefT PoeVQ3w&NR=1 http://www.youtube.com/watch?feature=endscreen&v=MefT PoeVQ3w&NR=1 – http://www.youtube.com/watch?v=uaedzlrnBGY http://www.youtube.com/watch?v=uaedzlrnBGY – http://flymove.uni- muenster.de/Processes/Segmentation/SegPair/SegPairEst/Seg PairEstGes.html http://flymove.uni- muenster.de/Processes/Segmentation/SegPair/SegPairEst/Seg PairEstGes.html

11. HOMEOTIC GENES Master regulatory genes Specify the types of appendages and other structures that each segment will form Mutations produce flies with structures in incorrect places

12. Examples of Homeotic Mutations Normal adult fly Antennapedia mutant Bithorax mutant

13. Antennapedia Mutations Wild-type Mutants

14. HOMEOTIC GENES are master genes that regulate the expression of numerous other genes – Some of the regulated genes are regulatory themselves

15. Drosophila DEVELOPMENT REVIEW: Hierarchy of Gene Activity Maternal genes in cytoplasm of the egg Segmentation genes of embryo – Gap genes – Pair-rule genes – Segment polarity genes Homeotic genes of the embryo Other genes of the embryo

16. HOMEOTIC GENES all possess homologous segments – 180-nucleotide sequence = homeobox (HOX) – Which encodes 60-amino-acid homeodomain

17. Homeodomain Homeotic genes – encode for transcription factors that influence other developmental genes – all have a hox region (homeobox) – which folds into a protein called the homeodomain. Homeodomain is the DNA Binding region of the transcription factor

18. HOMEOTIC GENES Vertebrate genes homologous to the homeotic genes of Drosophila have maintained their chromosomal arrangement

21. Ultrabithorax Other interesting gene names in Drosophila http://jpetrie.myweb.uga.ed u/genes.html http://jpetrie.myweb.uga.ed u/genes.html Regulatin’ Genes song for fun: http://www.youtube.com/watch? v=9k_oKK4Teco http://www.youtube.com/watch? v=9k_oKK4Teco