On Biology - Assignment Example

(a). Based on the figure in the book, From cells to consciousness, the cau nucleus is above the thalamus, and is thus the most superior part of the basal ganglia. Most closely associated to caudate nucleus is the putamen, which is inferolateral to it. These two structures are collectively called the striatum, and inferior to them are the other parts of the basal ganglia: globus pallidus, subthalamic nuclei and substantia nigra. (b). The graph shows the average concentration (mM) of four candidate HD indicators (1-4) in (A) those without the gene variant for HD, (B) asymptomatic carriers, and (C) symptomatic carriers. Results indicate that the concentration of indicator 1 is greatest among group A subjects (around 9 mM) and least among group C individuals (around 7 mM). Lowered levels of indicator 1, around 8 mM, may thus be found in carriers that can pass the gene to its offspring, and further decline may indicate presence of disease. Similarly, the least concentration of indicator 2 is found among symptomatic carriers (around 8 mM), and not much difference is seen between the indicator 2 levels of A and B subjects (around 10 mM). Low levels of chemical 2 may thus be used to diagnose symptomatic HD. On the other hand, no significant difference was found in comparing levels of indicator 3 (around 2 mM) among the three groups. Because levels of chemical 3 remain unchanged between healthy and diseased states, it is not a suitable indicator of HD. Finally, increased levels of indicator 4 (around 6 mM) is observed among group C subjects, and there is not much difference found between the indicator 4 concentrations of group A and group B individuals. This implies that high concentrations of this chemical may indicate symptomatic HD. The graph thus suggests that among the four test chemicals, only 1, 2 and 4 have the potential as an indicator for HD and HD-carriers. (c). (i). Figure 2 shows that concentration of the chemical is inversely proportional to the SLS score, which means that lower levels of indicator X can be found in individuals with higher SLS score, and vice versa. (ii). First, it must be noted that the indicator used must be relatively lower among symptomatic patients than the carriers. Based on figure 1, such relationship can only be seen for indicators 1 and 2. Moreover, the concentration of indicator 2 among carriers is 10 mM. If figure 2 is a plot of indicator 2 levels, then most of the scatter of HD-asymptomatic individuals must be above and below 10 mM. However, as figure 2 shows, only one individual is found to have 10 mM concentration of indicator, and none of the other carriers have levels above 10 mM. Thus, by deduction, figure 2 is a plot of indicator 1 concentrations. (iii). Using the trendline, we can estimate a person with an SLS of 300 to have about 8.2 mM of indicator 1, while a person with an SLS of 550 have around 6.8 mM of indicator 1. (iv). Based on figure 2, a person with an SLS of 300 will most likely be asymptomatic carrier of HD. However, 2 out of 4 subjects with an SLS of 300 have symptoms of HD, so there should be an equal chance for a person with an SLS of 300 to be symptomatic HD. Still, because an SLS of 300 is relatively low, this will most likely present as asymptomatic. On the other hand, a high SLS like 550 will more likely be symptomatic as all subjects with that score manifest with HD. References The Open University, 2006. From cells to consciousness. 2nd ed. London: Open University. Read More