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Sterile Insect Technique
News: Researchers from California have developed CRISPR-based system to safely restrain mosquito vectors via sterilization. It is called the new precision-guided sterile insect technique, or pgSIT.
Sterile Insect Technique:
• SIT is an environmentally safe and proven technology to suppress wild populations.
• To further advance its utility, a novel CRISPR-based technology, termed precision-guided Sterile Insect Technique (pgSIT) is described.
• It is a new scalable genetic control system that uses a CRISPR-based approach to engineer deployable mosquitoes that can suppress populations.
• Males don't transmit diseases so the idea is to release more and more sterile males.
• The population of mosquitos can be suppressed without relying on harmful chemicals and insecticides.
• It alters genes linked to male fertility—creating sterile offspring—and female flight in Aedes aegypti, the mosquito species responsible for spreading diseases including dengue fever, chikungunya and Zika.
• PgSIT mechanistically relies on a dominant genetic technology that enables simultaneous sexing and sterilization, facilitating the release of eggs into the environment ensuring only sterile adult males emerge.
• The system is self-limiting and is not predicted to persist or spread in the environment, two safety features that should enable acceptance for this technology.
• pgSIT eggs can be shipped to a location threatened by mosquito-borne disease or developed at an on-site facility that could produce the eggs for nearby deployment.
• Once the pgSIT eggs are released in the wild, sterile pgSIT males will emerge and eventually mate with females, driving down the wild population as needed.
What is CRISPR?
• CRISPR technology is basically a gene-editing technology that can be used for the purpose of altering genetic expression or changing the genome of an organism. The technology can be used for targeting specific stretches of an entire genetic code or editing the DNA at particular locations.
• CRISPR technology is a simple yet powerful tool for editing genomes. It allows researchers to easily alter DNA sequences and modify gene function. Its many potential applications include correcting genetic defects, treating and preventing the spread of diseases and improving crops. However, its promise also raises ethical concerns.
• The technology behaves like a cut-and-paste mechanism on DNA strands that contain genetic information.
• The specific location of the genetic codes that need to be changed, or “edited”, is identified on the DNA strand, and then, using the Cas9 protein, which acts like a pair of scissors, that location is cut off from the strand. A DNA strand, when broken, has a natural tendency to repair itself.
• Scientists intervene during this auto-repair process, supplying the desired sequence of genetic codes that binds itself with the broken DNA strand.
• It becomes contentious when used in humans. Leading scientists in the field have for long been calling for a “global pause” on clinical applications of the technology in human beings, until internationally accepted protocols are developed. Studies highlighted that CRISPR-Cas9-edited cells might trigger cancer.
• It may increase the risk of mutations elsewhere in the genome in those cells.
• Many things are not clear like how we should determine which disease or traits are appropriate for gene editing. In addition, there are concerns with manipulating human embryos for own interest.