What is CRISPR?
CRISPER-Cas9 is a type of biotechnology that allows scientists to edit/delete certain sequences of DNA (genes). This technology was inspired by and adapted from CRISPR, short for Clustered Regularly Interspaced Short Palindromic Repeats, which is a naturally occurring defense system found in bacteria. CRISPR recognizes the invader, then slices up an invading virus's DNA (or RNA). Most commonly, CRISPR is coupled with the term "Cas9," or CRISPR associated protein 9, which is the first enzyme that was discovered to perform the DNA slicing in viral invaders.
How does it work?
CRISPR-Cas 9 technology works similarly to how the CRISPR operation works in bacteria. Scientists start by creating a small piece of RNA. This RNA piece has a short "guide" sequence which will allow it to bing to a specific target sequence of DNA. The RNA strand will also bind to the Cas9 associated protein. The RNA is used to recognize the DNA sequence, and the Cas9 enzyme slices the DNA at the targeted location (National Institutes of). Then, one of two things can happen: either the cell will use its own repair mechanisms to fix the portion of DNA that was cut, or, scientists will then insert a strand of human-engineered DNA in place of the sliced strand of DNA, which is the essence of genetic engineering.
For a more detailed explanation of how exactly CRISPR-Cas 9 works, check out the link under the "Simulation" page!
In 2018, a scientist named Dr. He Jiankui gathered 8 willing couples to participate in his effort to produce human babies from gene-edited embryos. One of these couples got pregnant with originally identical twins and He carried out his experiment with them.
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While still their embryos, the twins had been injected with a CRISPR construct that was intended to cause a 32-base-pair deletion in a gene called CCR5, causing the gene to produce non-functional copies of the CCR5 protein. It was thought that the common variety of HIV usually needed functioning CCR5 proteins in order to invade and infect T-cells, so people without any functioning CCR5 genes could not have HIV or contract AIDS. This idea was later proven wrong but served as the motivation for this experiment.
Lulu & Nana Experiment
For neither twin did the CRISPR construct do exactly what it was intended to do: cause the deletion of a specific string of 32 base pairs. Instead, they caused changes in the CCR5 genes that would lead to the production of nonfunctional proteins but not through the method He expected. So, CRISPR had not altered either twin's genes.
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This experiment was seen as ethically controversial in several ways, which will be further discussed under the "Ethical Guidelines" tab. The Xinhua News Service’s story which was published on Jan 21, 2019, says that the twins exist still, that their health statuses, as well as the health of the other pregnant woman in the study, were being monitored, and that He as well as ‘other relevant personnel and organizations’ would ‘receive punishment according to laws and regulations.'