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July 20 - August 22, 2023
Using powerful biotechnology tools to tinker with DNA inside living cells, scientists can now manipulate and rationally modify the genetic code that defines every species on the planet, including our own.
As long as the genetic code for a particular trait is known, scientists can use CRISPR to insert, edit, or delete the associated gene in virtually any living plant’s or animal’s genome.
this technology will—someday, somewhere—be used to change the genome of our own species in ways that are heritable, forever altering the genetic composition of humankind.
What will we, a fractious species whose members can’t agree on much, choose to do with this awesome power?
DNA: A, G, C, and T, shorthand for the chemical groups (also known as bases) of adenine, guanine, cytosine, and thymine that distinguish the four compounds.
The letter A from one strand always pairs with T on the other strand, and G always pairs with C. These are known as base pairs.
each specific sequence of letters provides instructions to produce a particular protein inside the cell. The proteins then go on to carry out most of the critical functions in the body,
cells use a crucial—and closely related—intermediary molecule called ribonucleic acid, or RNA,
RNA, the letter T (for thymine) is replaced with the letter U (for uracil). In addition, the sugar that makes up the backbone of RNA contains one more oxygen atom than the sugar in DNA (hence the name deoxyribonucleic acid).
Every three letters of RNA, when read together, equal one amino acid, and amino acids are the building blocks of proteins.
This overall flow of genetic information—from DNA to RNA to protein—is known as the central dogma of molecular biology, and it is the language used to communicate and express life.
The human genome comprises about 3.2 billion letters of DNA, with around 21,000 protein-coding genes.
The human genome also includes a separate mini-chromosome—just sixteen thousand letters of DNA—located in mitochondria, the energy-producing batteries of the cell. Unlike the genetic code found in other chromosomes, mitochondrial DNA is inherited exclusively from the mother.
Scientists have precisely identified well over four thousand different kinds of DNA mutations that can cause genetic disease.
pioneers of this early gene therapy realized they could use viruses to deliver therapeutic genes to humans.
to a region of bacterial DNA and that the acronym stood for “clustered regularly interspaced short palindromic repeats.”
(Bacteria, Archaea—referred to collectively as prokaryotes—and Eukarya constitute the three domains that encompass all life on earth.)
CRISPR functioned like a molecular vaccination card: by storing memories of past phage infections in the form of spacer DNA sequences buried within the repeat-spacer arrays, bacteria could use this information to recognize and destroy those same invading phages during future infections.
The crucial components for DNA cutting were the Cas9 enzyme, the CRISPR RNA, and the tracrRNA.
For any twenty-letter sequence the guide RNA contained, Cas9 would find its matching counterpart in DNA and then cut.
In a short time, we had constructed and validated a new technology that, based on the body of research conducted with ZFN and TALEN proteins, would be capable of editing the genome—any genome, not just one belonging to a bacterial virus. Out of this fifth bacterial weapons system, we had built the means to rewrite the code of life.
downright dangerous.
Rallying cries have centered on a small handful of studies that claimed to reveal adverse effects on consumer health or the environment—for example, stating that GMO potatoes gave rats cancer and that GMO corn killed monarch butterflies—but these reports have been discounted in numerous follow-up studies and condemned by the broader scientific community.
near-unanimous consensus that GM food is every bit as safe as conventionally produced food.
Gene editing is now being harnessed to shut down pig genes that might provoke the human immune response and to eliminate the risk that porcine viruses embedded in the pig genome could hop over and infect humans during transplantation.
Oppenheimer said: “It is my judgment in these things that when you see something that is technically sweet, you go ahead and do it and you argue about what to do about it only after you have had your technical success. That is the way it was with the atomic bomb. I do not think anybody opposed making it; there were some debates about what to do with it after it was made.”
The “Berg letter,” as it’s often called, issued an unprecedented summons for a worldwide moratorium on experiments the committee deemed most hazardous—those aimed at creating antibiotic resistance in new bacterial strains and those aimed at creating DNA hybrids with cancer-causing animal viruses.
would be linked to us?
Every time our cells duplicate their DNA during cell division, somewhere between two and ten novel DNA mutations creep into the genome. Every person experiences roughly one million mutations throughout the body per second, and in a rapidly proliferating organ like the intestinal epithelium, nearly every single letter of the genome will have been mutated at least once in at least one cell by the time an individual turns sixty.
research in mice has demonstrated that eggs and sperm can be grown in the laboratory from stem cells and used to establish pregnancies. By eliminating disease-causing mutations with CRISPR and exhaustively screening for off-target mutations before the moment of fertilization, scientists could ensure that only those sex cells with the desired genome are used for reproduction.
When people refuse to acknowledge climate change, reject vaccination programs for children, or insist that genetically modified organisms are unfit for human consumption, it signals not only their ignorance about science, but also a breakdown in communication between scientists and the public.
