Rucete ✏ Campbell Biology In a Nutshell
Unit 3 GENETICS — Concept 20.3 Cloned Organisms and Stem Cells Are Useful for Basic Research and Other Applications
Cloning technology and stem cell research have profound implications for basic biology and medical applications. Organismal cloning creates genetically identical organisms, while stem cell technology has the potential to regenerate damaged tissues and treat various diseases.
Organismal Cloning: Plants
- In the 1950s, scientists cloned plants from single differentiated cells.
- Mature plant cells retain full genetic potential; they can "dedifferentiate" and regenerate an entire organism.
- This capacity is called totipotency.
- Widely used commercially and even at home (e.g., cuttings).
Organismal Cloning: Animals
- Somatic cell nuclear transfer (SCNT): Nucleus from a differentiated cell is inserted into an enucleated egg.
- The egg develops into a clone of the donor organism.
- Frog experiments (1950s–70s) showed that differentiated nuclei retain developmental potential.
- Dolly the sheep (1997) was the first adult mammal clone from a mammary cell.
- Dolly experienced health problems, likely from incomplete nuclear reprogramming.
Problems in Animal Cloning
- Clones often exhibit defects like obesity and premature aging.
- Caused by incomplete epigenetic reprogramming (e.g., methylation).
- Reprogramming the donor nucleus to reset gene expression is key for success.
Stem Cells: Embryonic and Adult
- Stem cells are unspecialized and can self-renew and differentiate.
- Embryonic stem (ES) cells: pluripotent, from blastocysts, can become nearly any cell type.
- Adult stem cells: found in tissues like bone marrow and skin, more limited in potential.
Medical Potential of Stem Cells
- ES cells can theoretically treat diabetes, Parkinson’s, spinal injuries, and more.
- Ethical concerns stem from destruction of human embryos.
Therapeutic Cloning and Induced Pluripotent Stem Cells (iPS)
- Therapeutic cloning: creates patient-matched ES cells via nuclear transfer.
- iPS cells: adult cells (e.g., skin) reprogrammed into pluripotent cells by introducing key genes.
- iPS cells avoid ethical issues and can differentiate into various tissues.
- Used for disease modeling, drug testing, and regenerative therapy.
- Research continues to improve safety, effectiveness, and affordability.
In a Nutshell
Cloning and stem cell technologies provide critical insights into developmental biology and offer revolutionary medical applications. While organismal cloning faces biological limitations and ethical debates, stem cell research—especially iPS cells—promises future therapeutic advancements personalized to patient needs.