DNA TECHNOLOGY: Part 1 Cloning & Stem Cell Research Nova video.
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DNA TECHNOLOGY: Part 1 Cloning & Stem Cell Research Nova video
What is a stem cell? Embryonic stem cell – An undifferentiated cell derived from embryos that have been fertilized in vitro and then donated for research. Not derived from eggs fertilized in a woman’s body. Adult stem cell – An undifferentiated cell found in a differentiated tissue that can give rise to all the specialized cell types of the tissue from which it originated. Not controversial. Undifferentiated cells are not yet specialized – they can become different types of cells.
Not all stem cells are created equal Princeton University Totipotent stem cells – can give rise to all types of tissue, i.e. an embryoall types of tissue Pluripotent stem cells – can give rise to most, but not all, tissues of an organism, i.e. inner mass cellsmost, but not all, tissues Multipotent stem cell – give rise to cells that have a specific function, i.e. blood stem cells *Potency = ability to differentiatespecific function What is a blastocyst? Is a blastocyst a human?
Where do stem cells come from? Human embryos (embryonic) In Vitro Fertilization (IVF) since late 70s Currently 4 million IVF babies alive Often creates extra embryos (~400,000 unregulated frozen embryos in U.S.) Somatic cells (adult) Cells are “reprogrammed” to be pluripotent
What’s cloning and how is it related? Therapeutic cloning (stem cell therapy)- Duplicating part of a person/organism e.g. a heart or liver, or even just a few cells. Reproductive cloning- Duplicating an organism e.g. identical twins.
Therapeutic cloning can be patient-specific (cells from patient put in donated egg)! Resulting cells would be a perfect match Could treat many diseases (i.e. diabetes) as body would not reject cells as foreign Experts warned that there was a risk the cells could become cancerous.
Are there Human Clones? Natural twins - just after fertilization a zygote divides into a two- celled embryo. Each cell continues to divide, producing 2 individuals. According to new research, though identical twins share very similar genes, they ARE NOT identical (environmental & epigenetic factors) Epigenetic (chemical) markers that turn genes on and off. Accumulate due to diet, smoking, etc. Can cause diseases like cancer and influence behavioral traits
Artificial Twins: Artificial Embryo Twinning Occurs in a Petri dish instead of in the mother's body. Manually separating an early embryo into individual cells, and then allowing each cell to divide and develop http://www.abpischools.org.uk/resources/poster-series/images/clon02.png
Artificial Twins: Somatic Cell Nuclear Transfer Different approach than artificial embryo twinning, but it produces the same result: an exact clone of an individual. (Roslin Institute http://www.roslin.ac.uk/library/)
The SCNT Animal Clone: Dolly (Roslin Institute http://www.roslin.ac.uk/library/) Nucleus of a sheep’s egg with the nucleus of a cell from a sheep’s udder. SCNT produces live offspring less than 1 in every 100 attempts Dolly was born in 1996 and euthanized in 2003 after developing progressive lung disease Agricultural value
Cloning & Stem Cell News 1996 – Dolly born 1998 – First experiment with human stem cells 2001 – Bush restricts federal funding for embryonic stem-cell research 2002 – First cloned cat 2004 – Researchers grow stem cells from embryos using private funding 2005 – South Koreans exposed for lying about creating 1 st human clone 2006 – Scientists discover method to extract stem cells without destroying embryo (this may skirt “when does a human become a human” issue) 2007 – Human skin cells transformed into cells that look and act like embryonic stem cells (however, process may cause increased risk of cancer) 2007 – A mouse was cured of sickle cell anemia using stem cells 2009 – Obama overturns stem cell ban & offers federal funding for embryonic stem cell research, but opposes human cloning 2009 – Obama overturns stem cell ban & offers federal funding for embryonic stem cell research, but opposes human cloning 2009 - Frozen skin used to clone a subspecies of ibex that went extinct in 2000 (Jurassic Park is still not a reality – no appropriate surrogate mothers for long-dead species)
In small groups generate two lists: 1. The potential uses and benefits of cloning (therapeutic and reproductive) 2.The potential problems and arguments against cloning (therapeutic and reproductive) – Use your notes from the video and be prepared to share with the class
Potential uses and benefits of cloning (cells and organisms) Replacing organs and other tissues Treat a variety of conditions (Parkinson's disease, burns, heart disease, diabetes, arthritis, etc.) Understanding what causes cells to become “sick” Infertility Replacing a lost child Creating donor people Gene therapy Saving endangered species
Problems/arguments against cloning (cells and organisms) Low success rate (Dolly took 276 attempts) Tumors & genetic defects Pre-mature aging (genetic age) Massive quantities of human eggs required Less genetic variation Lack of knowledge Value of life (blastocyst) Problems with cloning? Low success rate (Dolly took 276 attempts) Tumours Genetic defects Over-growth syndrome Pre-mature ageing (genetic age) Massive quantities of human eggs required Reduction in adaptability – genetic uniformity Insertion of genes Lack of knowledge