Are ‘designer babies’ something we really want?

Ability to alter genetics of embyros remains limited but progress will bring big questions


A “designer baby” is a baby whose genetic make-up has been selected or engineered to ensure certain traits are present and/or to eliminate particular effects/defects. Such design is possible today only to a very limited extent, eg gender selection, and research recently published by Ehud Karavani and others explains why mastering the ability to produce designer babies on a comprehensive basis remains a long way off. Just as well probably as this whole area fairly bristles with unresolved ethical questions.

Comprehensive ability in this field, were it ever attained, would allow parents to choose their new baby’s intelligence, athletic ability, musical ability, sex, eye and hair colour, height, to eliminate/lower certain health risks, and more.

The current practical approach to genetic enhancement of embryos is through pre-implantation genetic diagnosis (PGD) of in-vitro fertilised (IVF) embryos. Sperm cells from the father are fused with egg cells from the mother in a petri-dish to produce embryos.

These embryos are genetically analysed and those showing the desired genetic characteristics are implanted in the uterus. An advance on this technology would also allow editing of the embryonic genome, but such editing is illegal everywhere genetic modification in human reproduction has been legislated on.

Human traits are determined both by genetics and by the environment. Our genes are very influential, eg twin studies report that up to 80 per cent of one’s intelligence, as measured by IQ, is genetically determined. Some traits are determined by a single gene, eg many relatively rare diseases such as cystic fibrosis, phenylketonuria and so on.

But most traits are influenced by multiple genes. Height and IQ are two such traits and much is known about the complex underlying genetics, particularly for height. Karavani et al’s research reported in Cell examined the success of the PGD/IVF approach in selecting for enhanced IQ or height.

The researchers used genome sequences from real people to calculate the genome profiles of embryos resulting from sexual pairings of these people. They assumed that each couple would have 10 embryos to choose from and they predicted the IQ or adult height for each embryo based on the variants of gene present in the simulated embryos. They assumed the embryo with the top score would be selected for implantation.

The results show the effects on these theoretical offspring are quite small. The largest IQ gain above the average of the embryos was only 2.5 points, and the largest increase in height above the average was only 2.5cm. To appreciate how little 2.5 IQ points is remember average population IQ is 100 and 68 per cent of the population fall between IQ 85 and IQ 115, between one standard deviation (15 IQ points) below the mean to one standard deviation above the mean.

And even these small increases are not guaranteed because of natural variability not accounted for in the known gene variants. Also, many couples get much fewer than 10 viable embryos after IVF. And attempting to maximise more than one trait at once would greatly further complicate embryo selection.

Commenting on these results, Dr Liz Ormondroyd, genetic counsellor and researcher at Oxford University said: “This computer simulation study shows that, for these complex characteristics, designer babies remain in the realm of science fiction.”

Although we are still a long way from being able to comprehensively design babies, research will no doubt continue apace and eventually much that is now “science fiction” will eventually become possible. Would it be good to freely use this new technology?

The Oxford bioethicist Julian Savulesco argues genetic enhancement of offspring is so good that parents have a moral obligation to avail of it. I feel relatively few people would agree with this. While one can appreciate the good in the therapeutic genetic repair of an embryo to correct a mutation that would result in disease, deliberately designing 7ft tall basketball players with IQs of 180 is another matter.

There are many substantial reasons to frown on the idea of designer babies. For instance, societies now significantly stratify socio-economically on health, life expectancy and morbidity. What further yawning gaps of inequality would open up if better-off people routinely bought expensive technology to genetically enhance their offspring, technology beyond the means of poorer people?

William Reville is an emeritus professor of biochemistry at UCC

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