By Fizza Zaidi
With recent advances in gene therapy, the futuristic possibility of customizing a child has inched closer. A designer baby is a colloquial term for a baby who has been genetically modified to have specific traits. In some cases, undesirable traits such as genetic diseases may be removed, or favourable traits like enhanced intelligence may be added. There are currently three possible ways to do this, all of which involve manipulating fertilized eggs before in-vitro fertilization (IVF). IVF is a complex series of procedures used to help with fertility or prevent genetic problems. It also assists with conception. IVF works by retrieving mature eggs from ovaries, which are then fertilized by sperm in a lab, before being transferred into the uterus. The methods through which one can have a designer baby are preimplantation genetic diagnosis (PGD), transcription activator-like effector nucleases (TALENS), and clustered regularly interspaced short palindromic repeats (CRISPR).
The first method, PGD, works by choosing between viable eggs preimplantation for the one that best satisfies what the parents want. It can be used to screen for diseases and genetic disorders and can even pre-determine gender. Embryos are first created in the laboratory and grown for five or six days depending on their requirements. A biopsy for PGD is then performed on the embryos by removing a few cells from the trophectoderm. The genetic material stored inside the cells is then tested for abnormalities, followed by the embryos then being transferred into the uterus. Data has been collected from hundreds of thousands of births in humans using PGD [3]. Follow up evaluations of children born after PGD, between 1995 and 2014, have shown no detrimental growth effects. In fact, the NCBI have found no evidence that PGD treatment increases the risk of congenital malformations.
The second method, TALENS, involves enzymes that can be designed to remove specific parts of DNA strands to prevent genetic disorders or congenital diseases. The section is then replaced, allowing edits to be made. In theory, this technique can be used to target any section of DNA. So far, it has been used to design plants, fuels, and pets, but it hasn’t been used in people yet. This technology can be used to help with diseases such as sickle cell anemia and cystic fibrosis, which are caused by a single gene being broken [2]. TALENS first find the broken gene. This is done by injecting TAL proteins, which can recognize a certain DNA sequence of adenine, cytosine, guanine and thymine. These are the four bases found in a DNA strand. The bases bond with each other to make up the rungs of the DNA ladder. Adenine pairs with thymine, and guanine pairs with cytosine. The next step is to cut the DNA where there is a mistake. Cutting the DNA is the role of endonucleases, otherwise known as restriction enzymes. Scientists then insert the right DNA sequence and the cells do the rest of the work. Cells can fix mistakes in their DNA using homologous recombination [2]. Homologous recombination is the exchange of genetic material between two strands of DNA that contain long stretches of similar base sequences. In regards to TALENS, this is used to knock out individual genes and replace them with the correct one. It is estimated that it will take five to ten years to see this technology used in humans.
The last method, CRISPR, is a process that was discovered in the DNA sequence of certain bacteria. Their DNA contains snippets of viruses that have previously attacked them to allow them to recognize any threat in the future. These are known as CRISPR arrays. The method by which this new DNA becomes a part of their own has been replicated to allow the modification of other DNA strands. This allows edits to be made in any part of the genome. It works in the same way as TALENS. Researchers create a small piece of RNA with a short guide sequence that attaches to a specific target sequence of DNA in a genome. DNA replicates and stores genetic information. It is a blueprint for all genetic information contained within an organism. RNA converts the genetic information contained within DNA to a format used to build proteins and then moves it to ribosomal protein factories. The RNA also binds to a CAS9 enzyme which cuts the DNA at the targeted location [4]. CRISPR can be used to treat single-gene disorders, as well as more complicated conditions such as cancer or HIV. This method was used by a scientist illegally in a highly controversial attempt to make his twin daughters immune to HIV.
Despite only one of these methods being available to humans, parents have the option of screening eggs for gender, appearance, intelligence, disease, and personality. The most common use is to screen for diseases [2]. Screening for other aspects is highly controversial and has ethical implications. With technologies such as TALENS and CRISPR, it would be possible to edit eye colour, hair colour, brain function, muscle mass, and many more advanced traits. This raises questions about individuality. If parents have the option to pick features and traits that they deem “desirable,” their children will not have the option to develop their own identity. Overall, there have been many advances with the concept of designer babies. They have many benefits such as being able to cure genetic disorders and complicated conditions. Designer babies have become so much more than a concept of science fiction; they have become a reality. However, the important question is, what should the limits be?
References
Base Pair. (n.d.). Retrieved from https://www.genome.gov/genetics-glossary/Base-Pair
Chu, C., Yang, Z., Yang, J., Yan, L., Si, C., Kang, Y., . . . Niu, Y. (2019). Homologous recombination-mediated targeted integration in monkey embryos using TALE nucleases. BMC Biotechnology, 19(1). doi:10.1186/s12896-018-0494-2
Designer Babies, PGD, Genetically Modified Babies, GM Baby. (2020, January 29). Retrieved from https://www.newhopefertility.com/designer-babies/
Editing our DNA with Molecular Scissors. (n.d.). Retrieved from https://genetics.thetech.org/editing-our-dna-molecular-scissors
Heijligers, M., Van Montfoort, A., Meijer-Hoogeveen, M., Broekmans, F., Bouman, K., Homminga, I., . . . De Die-Smulders, C. (2018, November). Perinatal follow-up of children born after preimplantation genetic diagnosis between 1995 and 2014. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6240547/
Preimplantation Genetic Diagnosis (PGD). (n.d.). Retrieved from https://www.givf.com/geneticservices/whatispgd.shtml#:~:text=PGD is a genetic test,a couple is at risk.
What are genome editing and CRISPR-Cas9?: MedlinePlus Genetics. (2020, September 18). Retrieved from https://medlineplus.gov/genetics/understanding/genomicresearch/genomeediting/