Announcements

1. Testing center scoring of multiple choice

2. Today: overview of a few applications of recombinant DNA technology and small group discussions of ethics of using this technology

3. Pre-lab questions for behavior lab (lab 13) due at start of lab next week

Southern blot analysis

RFLPs restriction fragment-length polymorphisms

Establishing linkage between a dominant trait and an RFLP allele

Amniocentesis

Chorionic Villus Sampling

CVS uses catheter in uterus to obtain fetal chorion tissue.

Diagnosis of -thalassemia Deletion by Southern Blotting

Restriction EnzymeCut Sites

• Autosomal recessive, decreased or absent -globin protein.• Mutant alleles have large deletions or point mutations.

Diagnosis of Sickle-Cell Anemia Substitution by Southern Blotting

Restriction Site Lostin Sickle Allele

Individuals with Severe Combined Immunodeficiency (SCID) Have no

Functional Immune System

Homozygous for a defective ADA gene in T cells.Bubble boy, David, lived until removed from isolationafter a bone marrow transplant to restore his immune system.

Gene Therapy Involves a Retroviral Expression Vector, Based on Moloney Murine Leukemia Virus

Infect T cells and return cells to patient.

Inserted Human AdenosineDeaminase Gene

Genes for viral replication removed

StrongpromoterLong Terminal

Repeat regionscause integrationinto host genome

Gene Therapy for SCID

Integration into

chromosome

The first patient (SCID): Ashanti de Silva, treated at 4, is now 15

• Additional Successes Reported in Science (2000) 288:669-672.

• Gene Therapy reviewed in Science (2000) 288:627-629.

Limits of Gene Therapy

• Circulating cells, e.g. lymphocytes, are easier to target than solid tissues.

• Integration of retroviral vectors only in host cells replicating their DNA.

• Many vectors illicit an immune response.• Insertion into genes can inactivate them.• Vectors can carry a limited amount of DNA.• New generation vectors are addressing these

problems.

Ethics of Gene Therapy

• Somatic Cell Therapy targets diseased cells of patient, not passed on to offspring.

• Germ Line Therapy alters germ cells, creates heritable change.

• Enhancement Gene Therapy for increased height, intelligence

“It would be unfair. Simply rude to create another race. A mummyfied race with no end. It would also be surprisingly stupid to even consider such a thing as to clone an entire human. We would be creating the " Surpirior Race " as few like to believe. Leaving God out of it, we would be create the End of the entire human race. And Clones WOULD be our End. To imagine something being created that would have a learning ability above our own, strength, and something that could easily become unstoppable, is by far,unthinkable,and incredibly stupid. They WOULD evolve into a higher state of life, and would eventually be uncontrollable, the human races end. Even to suggest that they would THINK like us is UNBELIEVABLE!!! Humans have bad steakes! By cloning something with bad streakes you'd end up with something with a bad streak...only smart enough to do whatever they wanted, and not get stopped. In my part....cloning parts is okay, but a whole human clone ....would be wrong.”

“My medical ethics students have been discussing the cloning issue...here are the class thoughts. Cloning of humans will be used for 2 reasons: Therapeutic and Reproductive Purposes. The Therapeutic benefit will be a positive and may lead to cures for parkinsons, alzheimers and other diseases; Reproductive benefit is more of a social benefit to limited number of individuals...such as parents wanting to clone a child who has died. The cloning issue provides a "slippery slope" ethics that began with Abortion Ethics in the 70's...which made abortion (killing of human/potential human life) legal...the moral issue will never reach closure and continues...the primary question...when does life begin and who has rights over this life continue to be debated from abortion to embryo research to prenatal diagnosis and continues with the cloning debate. Our society will continue to create legal decisions that weigh the benefit of the few versus the good of the group...what each person needs to remember is that making a procedure legal does not make it moral...only you can decide that!”