Doppelzygotic Twins and the Ethics of Genome Ownership: The Rest Is Science Investigates Cloning Possibilities

Episode at a glance

In this Rest Is Science episode, Hannah Fry and Michael Stevens explore a provocative idea: a doppelzygotic twin, where two zygotes could be identical at different times, potentially creating genetically identical individuals without a single split. The discussion dives into genetics, epigenetics, and what it would mean for identity, ownership, and law.

• Concept and mechanics of doppelzygotic twins and how it differs from conventional monozygotic and dizygotic twins
• Phenotype versus genotype and why appearance does not map perfectly to DNA
• Ownership of genetic material and cells after birth and after death, with case studies like Henrietta Lacks and Moore v Regents
• Legal landscape around gene patenting and the ethics of cloning across jurisdictions

Overview

The Rest Is Science hosts Ian Fry and Michael Stevens discuss a provocative concept called doppelzygotic twins, where two zygotes could be formed at different times yet end up with identical or near identical genetic sequences. They examine the biology behind twins, the limits of genetic identity due to epigenetics and mutations, and the speculative pathways that might allow essentially duplicate genomes to occur more than once in a population.

From twins to doppelzygotic twins

The episode recaps the standard routes to twins: dizygotic twins arising from two separate zygotes, and monozygotic twins arising from the splitting of a single zygote. The proposed doppelzygotic model imagines two zygotes becoming formed in such a way that the resulting individuals share an extraordinary degree of DNA similarity, albeit not guaranteed to be perfectly identical due to genetic recombination, epigenetic differences, and somatic mutations over time. The discussion emphasizes the difference between genome identity and phenotype, noting that even with the same genetic material, people can look and behave quite differently.

Numbers, probabilities and the gaze into the future

A central point concerns the sheer combinatorial space of human variation. The hosts discuss rough estimates suggesting tens of trillions of viable, unique progeny could exist for two individuals, with a rough birthday paradox logic showing that as few as around 10 million children might yield a pair with nearly identical genomes. The chance of two siblings sharing almost all DNA yet not being from the same zygote appears non neglible in principle, though practically improbable due to the myriad of variables in conception and development.

Genotype, phenotype and personal identity

The conversation pivots to how genome identity translates into real life. Differences in epigenetics, gene expression, fingerprints, and personal experiences ensure that even true genetic twins are not perfect duplicates. The hosts highlight real world differences such as unique fingerprints that arise in the womb and diverge over a lifetime, underscoring that genome alone does not define a person.

Ownership, consent and legal precedents

Legal questions loom large as the discussion pivots to what it would mean if a person could clone or otherwise duplicate their genome. Henrietta Lacks is used to illustrate issues of consent and ownership in biology. Her cancer cells, taken without permission, became the HeLa cell line, enabling countless medical breakthroughs while her family lacked health insurance and did not receive compensation. The Moore v. Regents of the University of California case further complicates ownership, as the California Supreme Court ultimately held that harvested cells could belong to institutions, not the individual from whom they were derived, to avoid slowing medical progress. The discussion also covers 2013 patent rulings that genes themselves cannot be patented when they occur in nature, though artificially modified sequences or related technologies may be patentable.

Cloning across borders and the ethics of a new frontier

The hosts note that reproductive cloning is illegal in many places, though not uniformly across all jurisdictions. They point out that some countries have more permissive rules than others and discuss the challenge of crafting forward looking policies when science rapidly advances. The episode closes with a reflection on who should guard our genetic identity and whether celebrities or public policy should play a role in preventing dystopian uses of cloning technology.