Ethical Issues of Gene Editing in Human Embryos
The risks of using CRISPR-Cas9.
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CRISPR-Cas9, a tool developed in 2013 by American scientist Jennifer Doudna, has sparked a revolution in genetic editing. This technology offers a promising solution to genetic diseases by allowing scientists to precisely edit DNA sequences. By providing an RNA template, CRISPR/Cas can cut specific DNA sequences, enabling scientists to add, delete, or replace elements within the target DNA sequence. This innovation has dramatically transformed the speed and cost of gene editing, offering hope for conditions ranging from cancer and AIDS to cystic fibrosis and COVID-19.
However, recent research has shed light on the risks associated with using CRISPR-Cas9 in early human embryos. Dr. Nada Kubikova, from the University of Oxford, conducted a study revealing significant concerns. While the technology efficiently targets embryo cell DNA, it often fails to make the necessary corrections to defective genes. Instead, it frequently results in permanent breaks in the DNA strands, potentially leading to further genetic abnormalities in the embryo.
Gene editing has already started to benefit children and adults with diseases caused by gene mutations, such as cystic fibrosis, cancer, and sickle cell disease. However, the potential to prevent many more inherited disorders lies in editing embryos before they implant in the womb. This is the only stage of development where CRISPR-Cas9 technology can ensure that every cell of the embryo is reached. Despite this potential, the uncertainty surrounding its safety has led to a ban on its use in embryos in most countries worldwide.
Dr. Kubikova's study involved fertilizing donated eggs with donated sperm to create 84 embryos, with 33 of them subjected to CRISPR-Cas9 editing. The results showed high efficiency in targeting DNA sites, with alterations detected in the majority of embryos. However, only a small percentage of these alterations were repaired using the clinically useful process of homology-directed repair. Instead, a significant proportion of broken DNA strands remain unrepaired, leading to the loss or duplication of large pieces of chromosomes. This raises concerns about the potential for serious congenital abnormalities in babies resulting from such embryos.
Moreover, the majority of cells repaired the DNA break using non-homologous end joining, which results in additional mutations rather than correcting existing ones. It's crucial to recognize that editing an embryo affects all its cells, including eggs or sperm, meaning that modifications can be passed down to future generations. Given the relatively new nature of the tools used for germline edits and their uncertain safety, approximately 30 nations, including the United States and many countries in Europe, have already prohibited germline editing.
The ethical implications of gene editing are vast and profound. Who should have the authority to decide which genes are edited? What are the potential consequences for society as a whole? These questions demand careful consideration as we navigate the possibilities and limitations of gene-editing technology.
As we continue to grapple with these ethical dilemmas, it's imperative to approach gene editing with caution and thoughtfulness. While the technology holds immense promise for addressing genetic diseases, we must ensure that its application is responsible and ethical. By doing so, we can work towards a future where gene editing contributes positively to human health while minimizing harm and respecting ethical principles.
Written by Faiza Quader
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