Transcript Control of Gene Expression

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 techniques 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