Molecular Basis for Relationship between Genotype and Phenotype

1. Molecular Basis for Relationship between Genotype and Phenotype genotype DNA DNA sequence transcription RNA translation amino acid sequence protein function phenotype organism

2. Transgenesis • Introduction of foreign genetic material into a host organism. • 2. Ability of the new genetic material to be • transmitted to offspring of the host. • 3. Potential of the new genetic material to • be expressed in the host. • 4. Transgenic animals or transgenic plants • are the result of this process.

3. Gene Therapy Germ-line Therapy vs Somatic Therapy

4. Gene Therapy in Mammals

5. Human Gene Therapy • Approaches to treatment of diseases • DNA transfer into afflicted individual

6. 1990 : First Clinical Trial Severe Combined Immunodeficiency (SCID) - defective adenosine deaminase (ADA) gene. - afflicted patients express no functional T or B lymphocytes. - “Bubble Boy Disease”

7. Delivery Approaches to Somatic Therapy • Direct Administration: • Introduction of normal gene using a virus • retrovirus • adenovirus • Indirect Administration: • Reintroduction of cells that have been made transgenic

8. Criteria for Gene Therapy: Candidacy of a Disease for Consideration 1. Mendelian inheritance 2. One gene product for the gene 3. Knowledge of function of gene product 4. Availability of normal gene sequence 5. Localized symptoms for the disease 6. Availability of delivery system

9. ~ 25,000 genes in humans are potential candidates for gene therapy.

10. Candidates for Gene Therapy ?

11. ~ 25,000 genes in humans are potential candidates for gene therapy.

12. Cystic Fibrosis Disease is usually fatal. Lungs, other organs are clogged with mucus. repeated bouts of pneumonia heart stressed by decreased lung capacity delivery failure of pancreatic enzymes Life expectancy of 20-25 years ~1 of 29 Caucasians are carriers ~1 of 1600 Caucasians are affected ~30,000 Americans are affected

13. Cystic Fibrosis • Caused by recessive mutation (chromosome 7) • Failure to pump Cl- ions across cell membrane • Missing Cl- ion channel protein (cystic fibrosis • transmembrane protein or CFTR) • Normal gene sequence available (cloned in 1989) • Normal gene 250 kb in size • Transcript of 6 kb in size • Gene product of 1480 amino acids in length • Over 1500 mutations documented

14. Cystic Fibrosis as Candidate for Gene Therapy 1. Recessive gene on chromosome 7. 2. CFTR is the gene product. 3. CFTR is an ion channel protein. 4. Normal gene sequence has been cloned. 5. Symptoms are localized to specific organs. 6. Adenovirus (cold virus) can be used to deliver normal sequence to lung cells.

15. Transgenesis • Introduction of foreign genetic material into a host organism. • 2. Ability of the new genetic material to be • transmitted to offspring of the host. • 3. Potential of the new genetic material to • be expressed in the host. • 4. Transgenic animals or transgenic plants • are the result of this process.

16. Agrobacteriumtumefaciens (soil bacterium) causes crown gall disease in infected plants. Ti (tumor-inducing) plasmid is 200-kb double-stranded circular DNA. T-DNA region is transferred and randomly inserted into host plant genome. T-DNA directs tumor production and synthesis of opines, compounds that the bacterium needs for growth.

17. Genetic Engineering in Plants using Ti Plasmid T-DNA can be replaced by DNA sequence of interest and introduced into host plant genome. Reporter genes (selectable markers) are spliced into the recombinant T-DNA. Successful integration is indicated by expression of reporter genes. Refer to Figure 10-24, Griffiths etal., 2015. Markers (reporter genes) such as kanamycin resistance gene are very useful in monitoring successful transformation.

18. Generation of a Transgenic Plant Refer to Figure 10-25, Griffiths etal., 2015.

19. Genetic Engineering in Plants Plants that have been transformed include horse-radish, morning glory, cucumber, carrot, yam, cotton, sunflower, lettuce, tomato, corn, soybean, alfalfa, tobacco, potato, and clover. Agriculturally important crops can be engineered to express: - viral resistance - pesticide resistance - herbicide resistance - insect resistance Nutritional value can be enhanced, for example, by introduction of genes that increase seed protein content. Plants can be engineered to produce pharmaceutically important proteins or vaccines. Luciferase gene is useful as a reporter gene for transformation.