NOVA LABS The Evolution Lab / MISSION 5 wn of a moderm pandemic: Vinuses are str
ID: 199483 • Letter: N
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NOVA LABS The Evolution Lab / MISSION 5 wn of a moderm pandemic: Vinuses are strango. and the more we learn about them,the stranger they seom to get Considered by many as not quite an "organism because they can't reproduce heir own energy viruses are everywhere-on every surface and inside every living thing. Contrary to what most people think, however, many viruses are harmiless. Some are ikely even helpfull HIV, however, is not harmloss-at least not to humans. Where did it come from? Figuring that out is your job below before you move on to the next mission, "You Evolved. Too outside of a host or generate in this level. Answer questions 11-15 234&67 10 121334 Chimp SNM 11. A Cameroonian woman living in Paris was the first to be diagnosed with HIV-1 P in 2009. Which ape virus is most closely related to HIV-1 P? 12. Based on your completed tree, how can you distinguish HIV-1 M from HIV-1 N? a HIV-1 Mhas a C at poston 1,HIV-1 N has an A b. HIV-1 M has c. HIV-1 M has a G at position 14; HIV-1 N has a T d HIV-1 M has a T at position 7. HIV-1 N has an A an A at position 11, HIV-1 N has a G. 13. How do scientists think that SIV has jumped hosts to humans? 14. Based on your phylogenetic tree, how many times-at a minimum-do you infer that an HIV virus has jumped hosts to humans? Explain your answer 15. Viruses such as HIV reproduce rapidly. What is the connection between reproduction rate and evolution? 21Explanation / Answer
11. The most common strain of the Human Immunodeficiency Virus (HIV) is the HIV-1 M group of viruses. Besides HIV-1, here are other strains of HIV-1 virus which include HIV-1 N, HIV-1 O and HIV-1 P. These are rarer strains of HIV, and while HIV-1 O has been found to affect a small fraction of the population of western and central Africa, groups N and P have been found to be responsible for AIDS (caused by HIV-1) in Cameroon. Analysis of the HIV-1 P sequence has revealed that it bears a great sequence similarity with the simian immunodeficiency virus (SIV) found in wild gorillas : SIVgor. There is also a great degree of similarity in sequence with the SIV of chimpanzee : SIVcpz.
12. Based on the tree, the difference between HIV-1 M and HIV-1 N lies in the first position of the sequence. HIV-1 M has an Cytosine (C) in the first position whereas the HIV-1 N strain bears an Adenine (A) base in position 1.
13. The SIV (simian immunodeciency virus) originated in the great apes, but has been found to infect human hosts as well. How the SIV jumped from the great apes to humans is not clealry known, though scientists theorize that the SIV gene entered the human system through infected blood in the meat of the great apes. Early men have been known to hunt and feed on chimpanzees and non-human primates, who were susceptible to infection by the SIV. Though immunodefiviency genes are quite distantly related, there are some distinct similarities between SIV and HIV. Therefore, it is possible that the SIVcpz gene entered the human body through food and underwent mutation to turn into HIV.
14. The human immunodeficiency virus (HIV) gene is known to have originated in non-human primates in central and western Africa, which happened to later jump into human hosts from the former primate hosts. Based on the studies of viral mutation rates in HIV sequences preserved in human samples, scientists have estimated this jump from chimpanzee/gorilla to human to have occurred during the late 19th to early 20th century. This, as stated earlier, is theorized to have occured throught the intake of the meat of the great apes by humans, which might have contained blood contaminated with HIV. Thus, one jump of the HIV from non-human primates to humans, followed by mutation from SIV to HIV, led to the establishment of the SIV as the lethal immunodeficiencty virus in humans. The jump from one host to another and adapting to the new host requires mutations in the parasite genome (in this case the HIV). Therefore, mutation studies are an effective way of estimating the number of jumps that the HIV gene has gone through before arriving into the human system.
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