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More than a year ago, the world was shocked by Chinese biophysicist He Jiankui's attempt to use CRISPR technology to modify human embryos and make them resistant to HIV, which led to the birth of twins Lulu and Nana.
Now, crucial details have been revealed in a recent release of excerpts from the study, which have triggered a series of concerns about how Lulu and Nana's genome was modified.
CRISPR - Technique - Scientists - Edits - DNA
CRISPR is a technique that allows scientists to make precise edits to any DNA by altering its sequence.
When using CRISPR, you may be trying to "knock out" a gene by rendering it inactive, or trying to achieve specific modifications, such as introducing or removing a desired piece of DNA.
Gene - CRISPR - System - Relies - Association
Gene editing with the CRISPR system relies on an association of two proteins. One of the proteins, called Cas9, is responsible for "cutting" the DNA. The other protein is a short RNA (ribonucleic acid) molecule which works as a "guide" that brings Cas9 to the position where it is supposed to cut.
The system also needs help from the cells being edited. DNA damage is frequent, so cells regularly have to repair the DNA lesions. The associated repair mechanisms are what introduce the deletions, insertions or modifications when performing gene editing.
Jiankui - Colleagues - Gene - CCR5 - HIV
Jiankui and his colleagues were targeting a gene called CCR5, which is necessary for the HIV virus to enter into white blood cells (lymphocytes) and infect our body.
One variant of CCR5, called CCR5 Δ32, is missing a particular string of 32 "letters" of DNA code. This variant naturally occurs in the human population, and results in a high level of resistance to the most common type of HIV virus.
Jankui - Team - Mutation - CRISPR - Embryos
Jankui's team wanted to recreate this mutation using CRISPR on human embryos, in a bid to render them resistant to HIV infection. But this did not go as...
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