What are In Vitro Fertilization and Embryo Screening?

• In Vitro Fertilization (IVF)

– Sperm and egg united in a petri dish, followed by implantation of embryo(s) into mother’s uterus; pioneered by Robert Edwards as a treatment for infertility (Nobel Prize, 2010); roughly 20-30% success rate with a single embryo

– First “test-tube baby” (Louise Brown) born 25 July, 1978; more than 4 million babies born via IVF; controversies include multiple births (ex. octuplets) and un-used embryos

• Embryo Screening– Cells from embryo harvested in lab (vs. amniocentesis with a fetus),

and subjected to karyotyping and DNA fingerprinting– Pre-implantation genetic diagnosis (PGD): testing for genetic

conditions before an embryo is chosen to be used; allows bone-marrow match for other sibling (e.g. My Sister’s Keeper)

Fig. 7.19a

How are Clones Produced?

How are Clones Produced?

How are Clones Produced?• Cloning Techniques

– Enucleated egg cell implanted with donor nucleus (frogs and mice) or fused with 8-cell blastocyst (lamb, cow, pig, and monkey)

• Success rate is typically low, but improving (ex. Gaur, early 2001: 44 embryos in 32 surrogate cows led to eight pregnancies, only one successful)

• Questions over health of clones: lung problems; early aging suspected

• Success rate using adult donor cells varies by cell type (“Dolly” was from mammary gland cells)

• Success rate increased by incubation of donor nucleii in oocyte cytoplasm

What Are the Potential Applications of Cloning?

• Therapeutic Cloning– Affected individual (ex. paralysis) cloned, resulting embryo

used as a source of embryonic stem cells (overcomes rejection problem common with organ donations)

• Cloning Organisms (Reproductive Cloning)– Conservation of endangered species (to increase

population from critically low population)• Resurrection of extinct species (?)

– Cloning deceased pets – Increased efficiency of biotechnology

• Transgenic animals can be cloned• Production of genetically engineered organs that reduce rejections

– Human reproduction when other techniques have failed (child would be genetically related to only one

parent)

Mammals Cloned 1997-2007

What are Stem Cells?• Embryonic and Adult Stem Cells

– Embryonic: totipotent, can be cultured stem line; can be obtained from fertility clinics (un-used embryos), or from umbilical tissue (companies store cord blood)

– Adult: success varies by cell type; typically not totipotent, and potency may not last; not easily cultured, but tech-niques improving (cells re-programmed to embryonic state)

• Potential Uses of Stem Cells– Possible treatments of diseases involving dead or

damaged cells (spinal damage, Alzheimer’s, and Parkinson’s); success in several cases with mice; concerns regarding possibility of implanted cells becoming cancerous

– From 2000-2008 in U.S., publicly funded research allowed only on existing stem-cell lines (some leading specialists relocated to places like Singapore); recent changes under Obama Administration challenged in the courts