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

2. Germ-line Therapy vs Somatic Therapy
Gene Therapy
Germ-line Therapy vs Somatic Therapy

3. Gene Therapy in Mammals

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

5. Severe Combined Immunodeficiency
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”

6. 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

7. 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

8. ~ 25,000 genes in humans are potential candidates for gene therapy.

9. Candidates
for
Gene Therapy ?

10. ~ 25,000 genes in humans are potential candidates for gene therapy.

11. Disease is usually fatal. Lungs, other organs are clogged with mucus.
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 years
~1 of 29 Caucasians are carriers
~1 of 1600 Caucasians are affected
~30,000 Americans are affected

12. 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

13. 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.

14. Human DNA Information: Who should have access to your DNA information?
Ethical Concerns
Who should have access to your DNA information?