Transcribed Image Text: Answer the two questions below by reading the article
1, What was discovered in this article and how is it interesting
2, How is this discovery in the article related to genetics
Article
The novel SARS-CoV-2 coronavirus that emerged in the city of Wuhan, China, last year and
has since caused a large scale COVID-19 epidemic and spread to more than 70 other countries
is the product of natural evolution, according to findings published today in the journal Nature
Medicine.
The analysis of public genome sequence data from SARS-CoV-2 and related viruses found no
evidence that the virus was made in a laboratory or otherwise engineered.
"By comparing the available genome sequence data for known coronavirus strains, we can
firmly determine that SARS-CoV-2 originated through natural processes," said Kristian
Andersen, PhD, an associate professor of immunology and microbiology at Scripps Research
and corresponding author on the paper.
In addition to Andersen, authors on the paper, "The proximal origin of SARS-CoV-2," include
Robert F. Garry, of Tulane University; Edward Holmes, of the University of Sydney; Andrew
Rambaut, of University of Edinburgh; W. lan Lipkin, of Columbia University.
Coronaviruses are a large family of viruses that can cause illnesses ranging widely in severity.
The first known severe illness caused by a coronavirus emerged with the 2003 Severe Acute
Respiratory Syndrome (SARS) epidemic in China. A second outbreak of severe illness began in
2012 in Saudi Arabia with the Middle East Respiratory Syndrome (MERS).
On December 31 of last year, Chinese authorities alerted the World Health Organization of an
outbreak of a novel strain of coronavirus causing severe illness, which was subsequently named
SARS-CoV-2. As of February 20, 2020, nearly 167,500 COVID-19 cases have been
documented, although many more mild cases have likely gone undiagnosed. The virus has
killed over 6,600 people.
gins and evolution of SARS-CoV-2 by focusing in on several tell-tale features of the virus.
The scientists analyzed the genetic template for spike proteins, armatures on the outside of the
virus that it uses to grab and penetrate the outer walls of human and animal cells. More
specifically, they focused on two important features of the spike protein: the receptor-binding
domain (RBD), a kind of grappling hook that grips onto host cells, and the cleavage site, a
molecular can opener that allows the virus to crack open and enter host cells.
Evidence for natural evolution
The scientists found that the RBD portion of the SARS-CoV-2 spike proteins had evolved to
effectively target a molecular feature on the outside of human cells called ACE2, a receptor
involved in regulating blood pressure. The SARS-CoV-2 spike protein was so effective at
binding the human cells, in fact, that the scientists concluded it was the result of natural
selection and not the product of genetic engineering.
This evidence for natural evolution was supported by data on SARS-CoV-2's backbone -- its
overall molecular structure. If someone were seeking to engineer a new coronavirus as a
pathogen, they would have constructed it from the backbone of a virus known to cause illness.
But the scientists found that the SARS-CoV-2 backbone differed substantially from those of
Transcribed Image Text: already known coronaviruses and mostly resembled related viruses found in bats and
pangolins.
"These two features of the virus, the mutations in the RBD portion of the spike protein and its
distinct backbone, rules out laboratory manipulation as a potential origin for SARS-CoV-2" said
Andersen.
Josie Golding, PhD, epidemics lead at UK-based Wellcome Trust, said the findings by Andersen
and his colleagues are "crucially important to bring an evidence-based view to the rumors that
have been circulating about the origins of the virus (SARS-CoV-2) causing COVID-19."
"They conclude that the virus is the product of natural evolution," Goulding adds, "ending any
speculation about deliberate genetic engineering."
Possible origins of the virus
Based on their genomic sequencing analysis, Andersen and his collaborators concluded that
the most likely origins for SARS-CoV-2 followed one of two possible scenarios.
In one scenario, the virus evolved to its current pathogenic state through natural selection in a
non-human host and then jumped to humans. This is how previous coronavirus outbreaks have
emerged, with humans contracting the virus after direct exposure to civets (SARS) and camels
(MERS). The researchers proposed bats as the most likely reservoir for SARS-CoV-2 as it is
very similar to a bat coronavirus. There are no documented cases of direct bat-human
transmission, however, suggesting that an intermediate host was likely involved between bats
and humans.
In this scenario, both of the distinctive features of SARS-CoV-2's spike protein -- the RBD
portion that binds to cells and the cleavage site that opens the virus up -- would have evolved to
their current state prior to entering humans. In this case, the current epidemic would probably
have emerged rapidly as soon as humans were infected, as the virus would have already
evolved the features that make it pathogenic and able to spread between people.
In the other proposed scenario, a non-pathogenic version of the virus jumped from an animal
host into humans and then evolved to its current pathogenic state within the human population.
For instance, some coronaviruses from pangolins, armadillo-like mammals found in Asia and
Africa, have an RBD structure very similar to that of SARS-CoV-2. A coronavirus from a
pangolin could possibly have been transmitted to a human, either directly or through an
intermediary host such as civets or ferrets.
Then the other distinct spike protein characteristic of SARS-CoV-2, the cleavage site, could
have evolved within a human host, possibly via limited undetected circulation in the human
population prior to the beginning of the epidemic. The researchers found that the SARS-CoV-2
cleavage site, appears similar to the cleavage sites of strains of bird flu that has been shown to
transmit easily between people. SARS-CoV-2 could have evolved such a virulent cleavage site
in human cells and soon kicked off the current epidemic, as the coronavirus would possibly
have become far more capable of spreading between people.
Study co-author Andrew Rambaut cautioned that it is difficult if not impossible to know at this
point which of the scenarios is most likely. If the SARS-CoV-2 entered humans in its current
pathogenic form from an animal source, it raises the probability of future outbreaks, as the
illness-causing strain of the virus could still be circulating in the animal population and might
once again jump into humans. The chances are lower of a non-pathogenic coronavirus entering
the human population and then evolving properties similar to SARS-CoV-2.
Funding for the research was provided by the US National Institutes of Health, the Pew
Charitable Trusts, the Wellcome Trust, the European Research Council, and an ARC Australian
Laureate Fellowship.