The making of a human being - a minimalist view

It has always been a fact hard to explain why the male and female contribution to the production of a human being is so disproportionate.

While the hereditary material is roughly equal, the ovum is a hundred times larger than the sperm, the difference being due to the enormous quantity of material within the cytoplasm - a jelly-like substance packed with special proteins surrounding the nucleus.

As soon as the ovum is penetrated by the sperm, a frenzy of activity results. In particular the ovum is stimulated to make its last division, shedding off half of its chromosomes (found as a package called "a polar body", so that, like the sperm, it now contains only 23 chromosomes.

One would have thought that this miracle of organisation cannot be changed or altered in any way. There surely can be no shortcut or alteration. Surely the reproductive cells are so unique that no substitution can be allowed. All wrong! Practically every step in the natural process has been shown to be either unnecessary or replaceable by other components. The carefully worked-out plan that Nature prepared can be short circuited or dispensed with entirely.

Take first of all the role of the sperm. No man would like to admit that his role in reproduction is redundant. Yet so it is. The fact is that human embryos can be started without the use of sperm at all. The much vaunted macho superiority of males has received a mortal blow.

What about the role of the female ovum? While not entirely dispensable, this cell can certainly lose its nucleus which can be replaced by that from practically any cell in the body and still produce a normal embryo. The nucleus of neither the ovum nor the sperm seem to be required.

What is certainly essential is having the normal component of chromosomes (46 in number) irrespective of whether they come from sperm/ovum combination, or from any other cell. The process of cloning refers precisely to the practice of starting an embryo using a foreign nucleus implanted into a bare ovum cell from which the nucleus has been removed. The latest news now is that the ovum itself can be kick-started into active division and growth through a simple device: a small electric shock!

Dr Paul de Sousa, working at the Roslin Institute in Edinburgh, of world fame for producing Dolly, the first cloned sheep, has just announced this development, which he believes is a milestone in the development of stem cells for research purposes. And as the shock is given when the ovum still has its full component of 46 chromosomes, the resulting embryo can get started on its road to development.

But what appears to be most surprising is the finding that the only special component which is required to start a new life in all this manipulation in vitro is the presence, not of a special nucleus, but of a cytoplasm which is unique to the ovum and found in no other cell in the body.

Where does all this lead us? It certainly opens a Pandora's box of ethical issues which are in urgent need of solution. Certainly no one is currently thinking of letting this process advance into an advanced stage of embryonic life and hence the prospect of having human beings produced by this means is still, thankfully, very remote.

A number of intriguing questions arise. Does the ovum deserve the respect and dignity we usually reserve to an embryo when all that differentiates one from the other is a mere electric pulse?

Is the ovum more deserving of such respect than the sperm or, for that matter, any other cell from the body which has no such potential of developing into an embryo?

What special ingredients are there in the cytoplasm rather than the nucleus of the ovum which allow it, uniquely, to respond to a shock, in a way no other cell can?

Since the nucleus of an ovum is replaceable by that from any other cell, but the cytoplasm isn't, can we say that the uniqueness of reproduction is a function of the cytoplasm and not the nucleus? Is stem cell research, which is the driving force behind all this frenetic research, allowable when it does not involve a human embryo, but only a stimulated ovum? In particular, would the destruction of such an ovum be equivalent to destroying a human embryo?

As has become customary, scientific research has leapt far ahead of ethical reasoning or legal provision. We as a society are getting more and more worried that science is running away from us at a far greater speed than we care for or can deal with.

Moratoria to prevent foolhardy scientists from trying to be the first in publishing more and more outrageous results seem to work in some countries but not in others. We are far from convinced that we can control the development of what we have started - a situation somewhat akin to that prevailing in the 1940s with respect to atomic physics.

Do we need an explosion before we start taking seriously the societal problems associated with scientific activity?