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Cas9 (or "CRISPR-associated protein 9") is an enzyme that uses CRISPR sequences as a guide to recognize and open up specific strands of DNA that are complementary to the CRISPR sequence. Cas9 enzymes together with CRISPR sequences form the basis of a technology known as CRISPR-Cas9 that can be used to edit genes within living organisms.
The history of coronaviruses is an account of the discovery of the diseases caused by coronaviruses and the diseases they cause. It starts with the first report of a new type of upper-respiratory tract disease among chickens in North Dakota, U.S., in 1931.
The timeline of the COVID-19 pandemic lists the articles containing the chronology and epidemiology of SARS-CoV-2, [1] the virus that causes the coronavirus disease 2019 and is responsible for the COVID-19 pandemic. The first human cases of COVID-19 occurred in Wuhan, People's Republic of China, on or about 17 November 2019. [2]
Human coronaviruses infect the epithelial cells of the respiratory tract, while animal coronaviruses generally infect the epithelial cells of the digestive tract. [42] SARS coronavirus, for example, infects the human epithelial cells of the lungs via an aerosol route [68] by binding to the angiotensin-converting enzyme 2 (ACE2) receptor. [69]
The COVID-19 pandemic (also known as the coronavirus pandemic and COVID pandemic), caused by severe acute respiratory syndrome coronavirus 2 , began with an outbreak of COVID-19 in Wuhan, China, in December 2019. It spread to other areas of Asia, and then worldwide in early 2020.
Coronavirus diseases are caused by viruses in the coronavirus subfamily, a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, the group of viruses cause respiratory tract infections that can range from mild to lethal.
See: Guide RNA, CRISPR. Complementary base pairing between the sgRNA and genomic DNA allows targeting of Cas9 or dCas9. A small guide RNA (sgRNA), or gRNA is an RNA with around 20 nucleotides used to direct Cas9 or dCas9 to their targets. gRNAs contain two major regions of importance for CRISPR systems: the scaffold and spacer regions.
SARS-CoV-2 is the seventh known coronavirus to infect people, after 229E, NL63, OC43, HKU1, MERS-CoV, and the original SARS-CoV. [105] Like the SARS-related coronavirus implicated in the 2003 SARS outbreak, SARS‑CoV‑2 is a member of the subgenus Sarbecovirus (beta-CoV lineage B). [106] [107] Coronaviruses undergo frequent recombination. [108]