Genes and Development

1. Genes and Development Chapter 16

2. Development • All the changes that occur during an organism’s lifetime • Cell specialization: Cell determination: specific patterns of gene activity Cell differentiation: final step of cell specialization

3. Morphogenesis • The development of the body plan • Requires two steps: • Cell differentiation • Spatial organization • These depend on: • Pattern formation, cell signaling, cell shapes, cell migrations • Regulatory genes that turn other genes on and off at appropriate times

4. Zygote • The fertilized egg that develops into all the specialized cells needed within a multicellular organism • Each specialized type of cell makes a unique set of proteins • This is true despite the fact that these cells show nuclear equivalence – in other words they have the same genes

5. Cloning • A new individual that is genetically identical • In plants: have been able to make a clone from somatic (body) cells of an adult plant • In animals: have produced clones by transferring the nucleus of a cell into an enucleated egg cell • 1996: Dolly – cloned sheep in Scotland • Other mammals have been cloned since • Problems: only 1% - 2% success rate; high incidence of genetic defects

6. Dolly the Sheep

7. Rainbow and CC

8. Human cloning • Reproductive cloning – goal is making a new individual… very controversial and ‘banned’ • Therapeutic cloning – goal is NOT making a new person but producing stem cells

9. Stem Cells • Undifferentiated cells that can divide to produce differentiated cells and retain the ability to reproduce themselves • Totipotent: potential to give rise to all body tissues • Pluripotent: more specialized; can give rise to many but not all types of cells

10. Stem cells… • Potential uses: • Cures for degenerative diseases such as Parkinson’s • Potential sources: • Unused human embryos from fertility clinics and newborn’s umbilical cord blood

12. Control of cellular DNA expression • Differential gene expression (Ch. 13) • Genomic rearrangements: physical changes in the structure of the gene eg: immune system cells do this in order to produce new antibodies in response to infection • Gene amplification: the copies of a particular gene are increased so that the amount of transcription of that gene can be increased

13. Genetic control of development: • Very similar controls exist in a wide variety of organisms: • The basic mechanism evolved early and has been maintained although modified • Maternal effect genes: • Organize the structure of the egg cell • Help establish the polarity of the embryo: dorsal/ventral and anterior/posterior • Homeotic genes: • Specify the developmental plan for each body part

14. Genetic control of development… • Induction: cell differentiation is influenced by interactions with neighboring cells • Chronogenes: involved in developmental timing • Apoptosis – programmed cell death • Eg: skin between human fingers

15. Cancer and Cell Development • All forms of cancer have one thing in common: no divisional regulation of cells • Tumor: a localized group of cells with uncontrolled cell division • Metastasis – cancer cells ‘escape’ and spread to other parts of the body • Tumors that can metastasize are malignant

16. Cancer and Cell Development… • Genes that control cell division: • Proto-oncogenes – normal genes that control cell division • Mutations can change these into oncogenes – cancer genes • Some viruses carry oncogenes • Tumor suppressor genes – also put the ‘brakes’ on cell division • Mutations can turn off these genes and therefore stop the suppression of a tumor