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Chapters 47 & 21

Chapters 47 & 21. Animal Development & The Genetic Basis of Development. DEVELOPMENT. An organism arises from a fertilized egg as the result of three related processes Cell division Cell differentiation Morphogenesis.

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Chapters 47 & 21

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  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.youtube.com/watch?v=ZeIyrInOnMc

  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 FACTORSsuch 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=MefTPoeVQ3w&NR=1 • http://www.youtube.com/watch?v=uaedzlrnBGY • http://flymove.uni-muenster.de/Processes/Segmentation/SegPair/SegPairEst/SegPairEstGes.html

  9. 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

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

  11. Wild-type Mutants Antennapedia Mutations

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

  13. 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

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

  15. 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

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

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

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