Gattaca, the 1997 film, depicts a future society in which children are conceived through genetic selection to ensure that they possess the best hereditary traits of their parents.
2023. It can be done and it is done.
Genome editing is as important as it is controversial. The ability to modify a person’s genes to add or remove particular physical traits is passing from science fiction to real science: Scientists are already exploring the possibility of altering genes that cause specific diseases and editing human embryos to remove genetic mutations that cause some conditions. We should do it?
Instead of correcting words, gene editing rewrites DNA, the biological code that makes up the instruction manuals of living organisms. With gene editing, researchers can turn off specific genes, correct harmful mutations, and change the activity of specific genes in plants and animals, including humans.
There are thousands of genetic disorders that can be passed from one generation to the next; many are serious and life-threatening. They are not rare: one in 25 children is born with a genetic disease. Among the most common are cystic fibrosis, sickle cell anemia, and muscular dystrophy.
Gene editing has already been used to modify people’s immune cells to fight cancer or be resistant to HIV infection. It could also be used to correct faulty genes in human embryos to prevent babies from inheriting serious diseases. This is controversial because the genetic changes could affect your sperm or eggs, meaning the gene edits and any negative side effects could be passed on to future generations.
Agriculture has jumped on gene editing. The procedure is faster, cheaper and more precise than traditional genetic selection. Using gene editing, researchers have created seedless tomatoes, gluten-free wheat, and mushrooms that don’t turn brown when they age.
Gene editing is also being used to make pig organs safe for transplantation into humans. Gene editing also allows scientists to understand precisely how individual genes work.
There are many ways to edit genes, but the big breakthrough is a molecular tool called Crispr-Cas9. It uses a guide molecule (the Crispr bit) to find a specific region in an organism’s genetic code, for example a mutated gene, which is then cut by an enzyme (Cas9). When the cell tries to repair the damage and turns off the gene. Also, to repair a faulty gene, scientists can cut out the mutated DNA and replace it with a healthy strand that is injected along with the Crispr-Cas9 molecules. Different enzymes can be used instead of Cas9, such as Cpf1, which can help edit DNA more effectively.
Genes are the biological templates the body uses to produce the structural proteins and enzymes needed to build and maintain tissues and organs. They are made up of strands of genetic code, indicated by the letters G, C, T, and A. Humans have about 20,000 genes arranged on 23 pairs of chromosomes, all coiled up in the nucleus of nearly every cell in the body. Only about 1.5% of our genetic code, or genome, is made up of genes. Another 10% regulate them, ensuring genes are turned on and off in the right cells at the right time, for example. The rest of our DNA is apparently useless.
The letters of the genetic code refer to the molecules guanine (G), cytosine (C), thymine (T) and adenine (A). In DNA, these molecules pair up: G with C and T with A. These “base pairs” become the rungs of the well-known DNA double helix. The damaged gene in cystic fibrosis is about 300,000 base pairs long, while the one that is mutated in muscular dystrophy is about 2.5 million base pairs long, making it the largest gene in the human body. Each of us inherits about 60 new mutations from our parents, most coming from our father.
In some of the earliest gene-editing trials, scientists collected blood cells from patients, performed the necessary gene edits, and then introduced the modified cells into the patients. It is a promising approach as a treatment for people with HIV. A similar approach can be used to fight certain types of cancer: Immune cells are harvested from patients’ blood and edited so that they make surface proteins that bind to and kill cancer cells. After editing the cells to make them anti-cancer, the scientists mass-culture them in the lab and reinject them into the patient. The advantage is that they can be checked before re-injecting to ensure that the editing process hasn’t gone wrong.
Modern gene editing is pretty precise, but it’s not perfect. The procedure can be a bit hit and miss. Even when Crispr gets to where it’s needed, edits can differ from cell to cell—for example, repairing two copies of a mutated gene in one cell, but only one copy in another. For some genetic diseases, this may not matter, but it may if a single mutated gene causes the disorder. Another common problem occurs when edits are made in the wrong place in the genome. There may be hundreds of these “inaccurate” edits that can be dangerous if they disrupt healthy genes or critical regulatory DNA.
Will continue.
To know more
Genetics. NIH.
Center for Genetics and Society.