"Edward L. Ferman - Best From F&SF, 23rd Edition" - читать интересную книгу автора (Ferman Edward L)

Each of these two cells divides again, and each of the four that results divides again and so on.
If, after the first cell division, the two offspring cells, for any reason, should happen to fall apart, each
offspring cell may then go on to develop into a complete organism of its own. The result is a pair of
identical twins, each with the same genetic equipment and each of the same sex, of course. In a sense,
each twin is a clone of the other.
There is no reason to suppose that this separation of offspring cells can't happen over and over, so
that three or four or any number of organisms might not develop from the original fertilized egg. As a
matter of practical fact, however, a mother's womb can only hold so much, and if there are multiple
organisms developing, each is sure to be smaller than a single organism. The more organisms that
develop, the smaller each one and, in the end, they will be too small to survive after delivery.
There are such things as identical triplets and quadruplets, but I doubt that any higher number of
infants would survive long after birth without the advantages of modern medical technique. Even then it is
hard enough.
Identical twins are very like each other and often display mirror-image characteristics. (I once had a
chemistry professor with his nose canted to the left. His identical-twin brother had his nose canted to the
right, I was told.)
It is also possible, however, though not usual, for a woman to bring two different egg cells to fruition
at the same time. If both are fertilized, two children will be born who are each possessed of genetic
equipment different from the other. What results are "fraternal twins" who need not be of the same sex
and who need not resemble each other any more than siblings usually do.
Consider the fertilized egg again. Every time it divides and redivides, the new cells that form inherit
the same genetic equipment possessed by the original fertilized egg.
Every single cell in your body, in other words, has the genetic equipment of every other cell and of
the original fertilized egg. Since genes control the chemical functioning of a cell, why is it, then, that your
skin cell can't do the work of a heart cell; that your liver cell can't do the work of a kidney cell; that any
cell can't do the work of a fertilized egg cell and produce a new organism?
The answer is that though all the genes are there in every cell of your body, they aren't all working
alike. The cell is an intricate assemblage of chemical reactions, chemical building blocks, chemical
products, and physical structures, all of which influence one another. Some genes are inhibited and some
are stimulated, in a variety of ways depending on subtle factors, with the result that different cells in your
body have genetic equipment in which only characteristic parts are working at characteristic rates.
Such specialized development begins in the earliest embryo, as some cells come into being on the
outside of the embryo, some on the inside; some with more of the original yolk, some with less; some
with first chance at absorbing nutrients from the maternal bloodstream, some with only a later chance.
The details are clearly of the greatest importance to human biology, and biologists just don't yet know
them.
Naturally, the ordinary "somatic cells" of an adult human body, with their genetic equipment working
only in highly specialized ways, cannot divide into a whole organism if left to themselves. Many body
cells, such as those of the muscles or nerves, have become so specialized they can't divide at all. Only the
sex cells, eggs and sperm, retain the lack of genetic specialization required to produce a new organism
under the proper circumstances.
Is there any way of unspecializing the genetic structure of somatic cells so as to allow them to
develop into a new organism?
 Well, the genes are contained in the nucleus of the cell, which makes up a small portion of the total
and is marked off by a membrane of its own. Outside the nucleus is the cytoplasm of a cell, and it is the
material in the cytoplasm that provides the various chemicals that help serve to inhibit or stimulate e action
of the genes.
Suppose, then, the nucleus of a somatic cell were surrounded with the cytoplasm of an egg cell.
Would the genetic equipment in the nucleus unblock, and would the egg cell then proceed to divide and
redivide? Would it go on to form an individual with the genetic equipment of the original somatic cell and,