Highlights Transgenics and Cloning
1. Transgenics and cloning are very techie sounding words that are frequently misunderstood/misused. The word 'clone', for example is usually pictured by non-scientists as an exact copy of an organism. While that is indeed a clone, scientists often use the word to deescribe something other than a multicellular organism. Examples include "cloning" DNA (meaning making millions of identical copies of a DNA fragment) or "cloning" bacterial cells (isolating a DNA colony on a plate).
2. Technologies related to reproduction have been around for a long time. In the animal breeding business, artificial insemination has frequently been used to use the sperm of a single desired male to impregnate many females. This has the advantage of spreading male gametes widely, but only more recently have technologies been available for using multiple female gametes in breeding programs.
3. Female gametes can be produced readily by inducing ovulation in females with hormones. The ovaries produce multiple eggs that are harvested and then fertilized in vitro with sperm from a desirable male. The fertilized eggs can then be either frozen for use later (using glycerol to prevent damage from crystallization in the freezing process) or implanted into surrogate females that carry the fertilized egg to term.
4. Modern genetic technologies, such as in vitro fertilization, frozen embryos, and cloning are tools for saving threatened organisms.
5. To make a clone of an entire organism, the nucleus from the cell of an organism to be cloned is inserted into an egg cell in place of the egg's nucleus. The egg engineered in this way will divide and use the genetic material in the nucleus to make a copy of the original organism. All it takes to do this is an undamaged nucleus. Using this technology, there is a possibility of resurrecting extinct species of animals for which there is tissue that is in good shape. Wooly mammoths are one category of organisms that has been discussed in this regard, as there is frozen tissue of them from Siberia.
6. Chimeras arise from mixing of embryonic cells of organisms. It is possible to do this in the laboratory (to make a hybrid mouse, for example) and it may happen in nature. It is thought that some humans may show evidence of hybridization arising from mixing of embryonic cells of twins.
7. Cloning of humans is illegal and unethical. Interest in embryonic stem cells is high, though, due to their ability to be transformed into any differentiated tissue. The technique is controversial because it involves harvesting of human embryonic cells. Several technologies aim to do the same thing without using embryonic stem cells. They include transforming a nucleus of a person into an egg cell and growing it, not as an embryo, but on a plate. Cells made in this way would be "clones" of the original person, but wouldn't be able to become a clone of the person, at least not easily. Those modified cells could be used to make organs, it is thought.
8. Another rather bizarre approach would make "headless" versions of clones and harvest them for organs.
9. No matter what aversion we may have to the technologies, there is likely to be interest in them as people need organ transplants and don't have any other ways of getting them.
10. Increasing the life span of humans will likely have a major impact on the Earth's resources. An important question to consider is the impact such advances would have. While some would argue we should not pursue this type of research, it is worth noting that average human lifespans have almost doubled in the past century, thanks to antibiotics and other scientific advances.
11. Transgenic organisms are those who have had an alteration made to their DNA. In humans, there is interest in treating genetic disease by inserting functional genes into cells to "fix" the non-functional ones a person might be born with. Example diseases that people would like to treat in this fashion include sickle cell anemia and cystic fibrosis. There are problems with doing this, though, as to be most effective, EVERY cell would have to get a copy of the "good" gene and disruptions of the DNA that cause problems should not happen. Early attempts to do this have met with limited success. In some cases, insertion of genes resulted in causing cancer, due to the inability to control where in the genome a gene gets inserted.
12. A very useful transgenic animal is the lab mouse. The reason is that genetic technology is available that allows one to delete genes readily from the mouse and see the effect these deletions have on the organism. Some genes, when deleted, cause death. These are essential genes. Other genes, when deleted cause changes in the appearance or activity of an organism. By making such deletions (creating what are called "knockout mice"), one can understand what a given gene does by seeing the physical effect its deletion has.