Biologi Dasar II Semester Genap 2015/2016 Tugas Terstruktur 2 TT1 - TOPIC 6 How Does the Immune System Respond to a Changing Pathogen?[Data from L. J. Morrison, et al., Probabilistic order in antigenic variation of Trypanosoma brucei,International Journal for Parasitology35:961-972 (2005) and L. J. Morrison, et al., Antigenic variation inthe African trypanosome: molecular mechanisms and phenotypic complexity,Cellular Microbiology1:1724-1734 (2009)].Natural selection favors parasites that are able to maintain a low-level infection in ahost for a long time.Trypanosoma, the unicellular parasite that causes sleeping sickness, is oneexample. The glycoproteins covering a trypanosome’s surface are encoded by a gene that isduplicated more than a thousand times in the organism’s genome. Each copy is slightlydifferent. By periodically switching among these genes, the trypanosome can display a series ofsurface glycoproteins with different molecular structures. In this exercise, you will interpret twodata sets to explore possible explanation about the benefits of the trypanosome’s evershiftingsurface glycoproteins and the host’s immune response.Part A: Data from a Study of Parasite Levels.This study measured the abundance of parasites in the blood of one human patientduring the first few weeks of a chronic infection.Part A: Interpret the Data1.Plot the data in the above table as a line graph. Which column is the independent variable,and which is the dependent variable? Put the independent variable on thex-axis.2.Visually displaying data in a graph can help make patterns in the data more noticeable.Describe any patterns revealed by your graph.
3.Assume that a drop in parasite abundance reflects an effective immune response by the host.Explain the pattern you described in question 2.Part B: Data from a Study of Antibody LevelsMany decades after scientists first observed the pattern ofTrypanosomaabundanceover the course of infection, researchers identified antibodies specific to different forms of theparasite’s surface glycoprotein. The table below lists the relative abundance of two suchantibodies during the early period of chronic infection, using an index ranging from 0 (absent)to 1.Part B: Interpret the Data4.Note that these data were collected over the same period of infection (days 4–24) as theparasite abundance data you graphed in part A. Therefore, you can incorporate these newdata into your first graph, using the samex-axis. However, since the antibody level data aremeasured in a different way than the parasite abundance data, add a second set ofy-axislabels on the right side of your graph. Then, using different colors or sets of symbols, add thedata for the two antibody types. Labeling they-axis two different ways enables you tocompare how two dependent variables change relative to a shared independent variable.5.Describe any patterns you observe by comparing the two data sets over the same period. Do
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