So-called designer babies genetically selected for looks and intelligence are still far from becoming a reality, scientists say.
New research published in the journal Cell indicates that human traits, such as height or IQ, are a result of multiple genes working together along with other non-genetic factors, making it a challenge to accurately select embryos for desired traits.
Hypothetically, the process of maximising the chance to have a designer baby would involve screening IVF embryos to look for genetic variants associated with the desired characteristics before they are implanted – a process known as preimplantation genetic screening (PGS).
This technique is currently used in reproductive medicine to identify genetic defects in embryos to prevent the risk of passing on an inherited disorder to an unborn baby.
At present, the use of PGS in the UK is highly regulated and follows a strict licensing regime based on serious health conditions.
For their experiments, the researchers from the Hebrew University of Jerusalem focused on genetic variants associated with IQ and height.
They ran computer simulations using genetic data from real people to create genomic profiles of hypothetical embryos.
The team worked on the assumption that each couple would have 10 embryos to choose from and the one with the top score would be selected for implantation.
They then predicted the IQ or adult height for each of the offspring based on the gene variants present in the genomes of the simulated embryos.
The results showed the expected advantages to be relatively small – with IQ increasing by three points on average and height increasing by three centimetres.
The researchers say even these results are not guaranteed, as “there is much about these traits that is unpredictable”.
Study author Shai Carmi, of the Hebrew University of Jerusalem, said: “If someone selected an embryo that was predicted to have an IQ that was two points higher than the average, this is no guarantee it would actually result in that increase.
“There is a lot of variability that is not accounted for in the known gene variants.”
The researchers also emphasise that there are other limitations to this technology – for example, the genetic variants associated with height and IQ applies mainly to people of European descent and would not work for non-Europeans.
It also said attempting to incorporate more than one trait would make embryo selection far more complicated as an embryo that ranks highest for IQ may rank lowest for height.
To confirm their predictions, the researchers then analysed the genetic data of 28 families with adult children.
They found that offspring they would have selected for having the greatest height based on gene variants was not always the tallest one in adulthood.
Commenting on the research, Dr Liz Ormondroyd, a genetic counsellor and researcher at University of Oxford’s Radcliffe Department of Medicine, who was not involved in the study, said: “It has long been feared that genetic information might be used to select embryos based on desire for characteristics such as increased height or intelligence.
“This computer simulation study shows that, for these complex characteristics, designer babies remain in the realm of science fiction.”
While designer babies based on looks and intelligence may be far off, a recent study by Abertay University in Dundee found that the risks of gene editing are now low enough to warrant its use with human embryos to treat common disorders, with scientists saying that “ethically sound” genetically modified babies could begin within two years.