Sunday, March 10, 2013
Virus
Big Ideas 1 (the process of evolution drives the diversity and unity of life) and 3 (living systems store, retrieve, transmit, and respond to information essential to life processes). What are viruses? Edward Jenner founded the first vaccine (on page 125); how did Jenner confirm his theory about cowpox preventing smallpox? Describe the effect a virus has to the immune system. On page 126, when Dr. Moalem states “genes could change” in order to create a large amount of antibodies, what does he mean by that? How are genes able to ‘change’?
Through evolution, the human body has adapted to many bacteria and viruses that have aided in the process of survival and reproduction. On page 129, Sharon explains how many of the bacteria and viruses that were once a threat and/or just independent, now make up a third of our DNA. One of these bacteria was the mitochondria. Describe the similarities and differences of being a prokaryotic versus eukaryotic cell. Explain how having viral and bacterial DNA can benefit or harm the human body. Provide an example of a antigenic drift and an antigenic shift (page 131).
Sigal Sasson
email: ssasson3@students.d125.org
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A virus is a small infectious agent that can only replicate inside the living cells of another organism. To humans, viruses can range anywhere from extremely deadly to harmless based off of the type of virus and the person's immune system. Viruses enter the body by bypassing the first line of defense, or physical barriers such as skin or mucus, that the body has. If the virus gets past the physical barriers, it has to get past internal defenses, first the inflammatory response, and then specific immune response, specifically cell-mediated, or antibody mediated responses. If none of these defenses are able to stop a virus, the virus can end up overrunning the person's cells by injecting its DNA into each host cell and replicating and bursting the host cell at the same time.
ReplyDeleteVaccines take advantage of how the immune system works by triggering active immunity in order to stimulate the immune system to produce antibodies to either attack a killed version of the virus and produce memory B cells so that the body can readily attack the same invading virus later or attack a similar, but slightly different, version of the virus so that the body has antibodies that are extremely close to the type needed for when the deadly virus attacks. Edward Jenner's theory about cowpox and smallpox is an example of the second type of vaccination. He was able to confirm his theory that catching cowpox could prevent smallpox when he "scraped a cowpox sore on an infected milkmaid and purposefully infected several teenage boys" … "The cowpox infection resulted in protection from smallpox" (125). The storing of the antibodies relates to Big Idea 3, living systems store, retrieve, transmit, and respond to information essential to life processes because the body takes the antibodies that already work and store them for later use.
When Dr. Moalem states that "genes could change" (126), he is referring to the immune systems process of creating a perfect fitting antibody to a specific virus. According to the Genetics Home Reference, "Acquired (or somatic) mutations occur in the DNA of individual cells at some time during a person’s life. These changes can be caused by environmental factors such as ultraviolet radiation from the sun, or can occur if a mistake is made as DNA copies itself during cell division." (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/genemutation). The immune system takes advantage of change in cells due to mistakes during copying when attacking a virus. By making millions of copies of an antibody that almost matches a virus, the body can get the duplicated antibodies to mutate due to chance to fit the virus perfectly. These mutations change the genetic makeup of the antibodies for the benefit of the body and relate to Big Idea 1, the process of evolution drives the diversity and unity of life because of how the antibodies adapt, even though they don't actually evolve into different organisms, to attack viruses.
Prokaryotic cells are very small with no nucleus and no membrane bound organelles that multiply through fission. Eukaryotes are larger cells with a nucleus, membrane bound organelles, and divdd through mitosis or meiosis. Viral and bacteria DNA can benefit the human body because they can be very helpful to the function of our cells. For example, mitochondrial DNA is incorporated into the human body, and "most scientists now believe that mitochondria were once independent, parasitic bacteria that evolved a mutually beneficial relationship with some of our pre-mammal evolutionary predecessors" (129). The mitochondria were once bacterial, so their DNA has been incorporated into ours to benefit us. Antigenic drift is when "a mutation occurs in the DNA of a virus" (131) and antigenic shift is when " a virus acquires new genes from a related strain" (131).
Tony Massat
amassat4@students.d125.org