Saturday, June 04, 2005

What is Cloning?

(This is part 4 of a series, which begins here...)

“Cloning”, in general, refers to the production of an exact copy of a living organism. Generally, when nature creates a clone, a large number of copies are made. The term is used to describe the normal process within our own body whereby a certain type of immune cell is made. Something to which we are becoming immune will change one of our immune cells, which “recognizes” the foreign substance as foreign and constructs an antibody to that substance. Then this cell that “knows” the foreign substance is replicated by the body over and over again, so as to generate an army of identical cells, all of which can make the new antibody. (Palpatine’s Clone Army writ small…) Likewise, most cancers are “clones” of one or a few cells that somehow lost their ability to govern their own reproduction and have begun to replicate themselves endlessly. The huge colonies of E. coli and other microorganisms that are used to produce human insulin and other human protein medications are clones of a bacteria cell into which was inserted a human gene, the “blueprint” for human insulin for example, and then that cell was “cloned” into billions of identical cells, all of which have the gene for insulin and make insulin along with their normal products. When we do bone-marrow transplants, or grow skin tissue on Petri dishes to treat burn victims, we are relying upon types of cloning processes, using adult stem cells in the case of the bone-marrow transplant.

The cloning that is controversial is the reproduction of human tissues from “embryonic” cells. I have used quotation marks to indicate that the term “embryonic” can have different meanings, which may be philosophically as well as technically distinct. We already clone bone marrow stem cells to replenish cancer victim’s cells that have been wiped out by chemotherapy or radiation. We already grow layers of skin on culture medium to treat burn victims. We already swap whole tissues and organs from one individual to another, from corneas to livers to hearts and lungs. We therefore have not evidenced a theological problem with “tissue ownership” or with growing tissues outside the body to be returned to the body of a victim as “repair” tissue, even if the tissue was not one’s own. The problem resides in the concept of “embryonic”, because we identify the embryo as being an individual human being, so that any manipulation or destruction of the embryo is seen as human mutilation or murder.

Let us look closely at this type of “cloning”, considering the reasons people are interested in it, and the processes involved at this time in the development of the technology.

The type of cloning we are considering is called somatic-cell cloning. A somatic cell is a cell that comes from body cells as opposed to reproductive cells. If we wanted to generate a whole group of identical persons, for example, we could start with a zygote fertilized in the normal way, by combination of sperm and egg, and then keep separating that little ball of cells over and over again to get identical twins, then identical quadruplets, then identical octuplets, etc. These individuals would all be identical to each other, but different from everyone else outside their birth-group because their genetic material came, originally, from a sperm-and-egg fertilization and is hence unique. This is not somatic-cell cloning, because it starts with the germ cells.

In somatic cell cloning, a nucleus is taken from some non-reproductive-system cell in a developed organism, and “reset” to the original pluripotent status characteristic of a zygote. That is, all the “librarians” in the library are instructed to close all the open drawers, and now unlock only those drawers with those blueprints that are opened to begin development of the whole body from scratch, ie, those drawers which are open in an embryo at the ball-of-cells stage. It is like pressing the “reset” button, so that now this cell, which previously could only develop into a bone or muscle cell, could now develop into any and every tissue in the body. Because this cell came from a certain donor individual and has all that individual’s genetic material, this means that any tissue that developed from this cell would be genetically and immunologically identical to the donor’s tissues, hence it would be accepted back into the donor’s body in the same way that his own skin cells can be accepted back after being grown in tissue culture. It is the promise of being able to grow such identical replacement tissues that makes somatic-cell cloning such a hot research item.

So, the goal in human cloning is to take a donor's differentiated, determined cell and reset its nuclear material back to the embryonic state, so that it can then develop into any human tissue that is needed. How might this be done? How to convince the “librarian” proteins to reset the library to Day 1? Scientists reasoned that there might be something in the environment of an egg that sets the nucleus to behave as an embryonic nucleus, so they began removing the unfertilized nuclei from eggs, sucking the nucleus out of a donor’s somatic cell (a skin cell, for example), and injecting it into the enucleated egg. I am simplifying greatly, but the idea is to use the cell-constructing machinery of the egg cytoplasm (the cell organs outside the nucleus that do the building) together with the instruction set of a particular donor’s unneeded somatic cell nucleus. Whatever molecules or combination of circumstances that obtain within an egg cell, they serve to reset the genetic code in the nucleus. One day, almost certainly, the exact identity and mechanism of action of these “resetting” proteins will be discovered, and at that point the somatic nucleus may not have to be placed into an empty egg cell, but perhaps “reset” in a test tube, within its own original cell membrane. It is important to understand that the use of evacuated eggs is, at this point, simply a crude technique to accomplish an intranuclear event: the un-determination of the somatic cell, a reversion to an earlier state in the developmental program.

One can easily see the cause of the most serious alarm among evangelicals: the status of the reset nucleus-egg cell as “embryonic”. If indeed this technique creates a “fertilized egg” that, if implanted in a womb, would develop into the donor’s twin, does it not become a separate “human being” at the moment the nuclear program is reset? Is it not just the same as all the other in-vitro embryos that are created in the various processes of technologically-aided fertility? Is it not the donor's "twin"? More next time….

(This series continues here...)

1 comment:

  1. Hi Joe,

    Thanks for your recent posts. I'm trying to follow along and I'm finding this quite informative. I'm all ears.

    Christie G.