Synthetic embryology vs. Genetically engineered embryo

Synthetic embryos are lab-grown from stem cells. By reprogramming stem cells, they can organize themselves into an embryo-like model that share a similar shape and function with real embryos. Because of the lack of sperm and egg cells, a synthetic embryo can never become a full-fledged living being, but these embryos work as a model of real embryos. These embryos have been used to study the “black box” period of embryo development, otherwise known as the two week period following fertilization of the egg. Due to their resemblance to real embryos without actually being one, these models have been used by scientists to understand potential causes of miscarriages, model diseases, or test drugs without ethical restraints.

Unlike synthetic embryos, genetically engineered embryos involve the usage of real embryos, or ones that have been formed through the fertilization of an egg by sperm. Scientists edit the genes within the embryo, using technology known as CRISPR-Cas9, before implanting it in a womb to continue growing. CRISPR-Cas9, which stands for Clustered Regularly Interspaced Short Palindromic Repeats, allows scientists to edit any gene as they please by adding, removing, or altering any sequence in almost any organism. The enzyme, Cas9, is located in the CRISPR system and works as a DNA-cutting protein. Cas9 can be controlled using guide RNA, which directs the protein to cut specified parts of a gene. This can be applied to genetically engineered embryos to root out the more “undesirable” parts of the genome, such as ones that code for genetic diseases. However, this technology can also be utilized to enhance “desirable” traits that may give the organism an advantage in the future; for humans, this essentially creates a “designer baby” if the embryo survives. This gives rise to many ethical concerns, especially taking into account that this is a living being, so genetically engineered embryos are banned or restricted in many places. 

The main difference between synthetic embryos and genetically engineered embryos is that it is biologically impossible for synthetic embryos to become a living organism in the future, while it is entirely possible for genetically engineered ones to survive past birth. This main difference gives rise to different uses for each, as well as different ethical questions.

References:

Devlin, Hannah. “Synthetic Human Embryos Created in Groundbreaking Advance.” The Guardian, 14 June 2023, www.theguardian.com/science/2023/jun/14/synthetic-human-embryos-created-in-groundbreaking-advance.

Ebrahimkhani, Mo R., and Michael Levin. “Synthetic Living Machines: A New Window on Life.” IScience, vol. 24, no. 5, May 2021, p. 102505, https://doi.org/10.1016/j.isci.2021.102505.

Ferguson, Kirsty. “In the Spotlight: The First Gene-Edited Babies | Eurostemcell.” Www.eurostemcell.org, 3 Apr. 2020, www.eurostemcell.org/spotlight-first-gene-edited-babies.

“Genetic Modification of Embryos - American Surrogacy.” Americansurrogacy.com, 2025, www.americansurrogacy.com/parents/genetic-modification-of-embryos.

Landecker, Hannah L., and Amander T. Clark. “Human Embryo Models Made from Pluripotent Stem Cells Are Not Synthetic; They Aren’t Embryos, Either.” Cell Stem Cell, vol. 30, no. 10, 5 Oct. 2023, pp. 1290–1293,

www.sciencedirect.com/science/article/pii/S1934590923003272?via%3Dihub, https://doi.org/10.1016/j.stem.2023.09.006.

MedlinePlus. “What Are Genome Editing and CRISPR-Cas9?” Medlineplus, National Library of Medicine, 22 Mar. 2022, medlineplus.gov/genetics/understanding/genomicresearch/genomeediting/.

“News: A Synthetic Embryo, Made without Sperm... (CNN News) - behind the Headlines - NLM.” NCBI, 2022, www.ncbi.nlm.nih.gov/search/research-news/17118/. Accessed 9 Mar. 2026.

Wikipedia Contributors. “CRISPR Gene Editing.” Wikipedia, Wikimedia Foundation, 6 May 2019, en.wikipedia.org/wiki/CRISPR_gene_editing.

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