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Embryos and pseudoembryos: parthenotes, reprogrammed oocytes and headless clones
  1. Helen Watt
  1. Correspondence to:
 Dr H Watt
 Linacre Centre for Healthcare Ethics, 38 Circus Road, London NW8 9SE, UK; h.watt{at}

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Recent proposals for creating “pseudoembryos” by different techniques and moral status of such entities

What makes something (or someone) an embryo—as opposed to what is actually, and not just in biotech parlance, a collection of cells? This question has come to the fore in recent years with proposals for producing embryonic (or pseudoembryonic) stem cells for research. While some of those opposed to use of standard embryonic stem cells emphasise that adult (including umbilical) cells have a clinical track record, others argue that there may be further benefits obtainable from cells very like those of embryos, provided such cells can be derived in new ways. Rather than deriving them in ways that kill or otherwise endanger a living human embryo, they could be obtained from an entity that merely resembles a human embryo sufficiently closely for its cells to be of use. Such an entity might be created after introducing genetic changes to an ovum before it is activated by, for example, a cloning-type procedure, such that a gene essential to embryogenesis will be either absent, blocked in its expression, or overexpressed.1,2 The claim is that the ovum could be made to give rise to embryonic stem cells—mere living parts—without ever giving rise to a whole embryo, who is killed to obtain them. Whereas cloning “proper” winds back the specialisation of the cell nucleus to a point where a whole embryo is formed who has not yet specialised its cells, oocyte-assisted reprogramming (OAR), it is claimed, would wind back the specialisation merely to an intermediate point at which no embryo is created. Other methods proposed for deriving pseudoembryonic cells include parthenogenesis, in which an ovum is activated without a sperm, or even the insertion of an adult cell nucleus.1


In this paper, I assume that a genuine …

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  • i Note that it is active potential—the power of an entity to act, while remaining the same entity456—which is in question here. The passive potential of a cell to be used to produce a different kind of entity is a separate phenomenon. True, embryonic cells are particularly plastic in terms of their ability to produce (or help produce) new organisms when isolated from and/or combined with other cells. We should, however, remember that adult cells can also be used to produce new living organisms, either by fertilisation or by cloning. Indeed, human adults, and even their gametes, have an active, not a mere passive potential to reproduce sexually—although they will forfeit their identity in the process in the case of gametes. Adult cells, like embryonic cells, can also be incorporated into existing organisms, as in stem cell research. The plasticity of a being’s parts—that is, their ability to be put to new uses—does not change what those parts now constitute, or any moral claims that being may have.

  • ii To say that the nuclear genes are necessary for the embryo’s existence is not, however, to say they are sufficient, or that the human organism is reducible to its genes.

  • Competing interests: None.