MIT Department of Biology 7.014 Introductory Biology, Spring 2005 Solutions to 7.014 Problem Set 1 Question 1 Please read the following two articles, and answer the questions at the end Article I Fouad, Tamer. "Laptops can affect fertility in males, US researchers warn."(January 1, 2005).(full text at http://www.thedoctorslounge.net/fertilounge/articles/fertility_laptops)Please refer to article:Article II 2Moore, Charles. "Hot Laptops A Male Reproductive Health Hazard - And SomethingYou Can Do About It." Road Warrior, January 4, 2005.(full text with pictures at http://www.macopinion.com/columns/roadwarrior/05/01/04/ )Please refer to article:Question 1 a) Do the articles above present the findings of the laptop study objectively? If yes, justify. If no, give examples of biased reporting and explain why you believe the reporting to be biased. (Feel free to underline or highlight passages in the text, as long as you clearly identify the meaning of your markings)The first article presents the findings objectively. The article describes procedure used in the study in great detail, and its report on the study’s conclusions is limited to those supported by the reported data. Article also relies heavily on direct quotes from the lead author of the study, ensuring a large degree of impartiality. The second article, on the other hand, overstates the reported results of the study to a large degree. For example, compare the quote highlighted in dark blue in the first article with the one highlighted in light blue in the second. While the first article merely reports elevated scrotum temperatures observed in the experiment, the second article makes a connection to reduced sperm production and fertility. This connection is not substantiated by data obtained in this experiment, or by an applicable previously reported experiment.Similarly, compare quotes highlighted in green and yellow. Notice the use of “may want to” in the first articlevs “should” in the second, and the truncated quote in the second article with respect to the first. b) Look again at the second article. Does the Laptop Desk study answer the question of how likely is it that this device would help alleviate the problem of the elevated scrotum temperature associated with laptop use? Why or why not? Reporting of the Laptop Desk study talks only about measuring the temperatures on the device itself. It gives no indication that the study involved measuring how effective the product would be in alleviating the problem of the elevated scrotum temperature associated with laptop use. To determine that, one would need to conduct a study where the scrotum temperatures were measured when using the Laptop Desk in various configurations with and without a working laptop computer. c) Based on the information in the two articles, do you think the Laptop Desk is likely to be a significant relief for the problem of the elevated scrotum temperature associated with laptop use? Why or why not? It is unclear from the data. The claim of the article is that the product would help alleviate the problem ofelevated scrotum temperatures by giving the user an option to sit with his legs open. It does not, however, measure what the scrotum temperature would be in such a configuration. A reasonable hypothesis might be that scrotum temperature would still be elevated due to the partially enclosed space and heat coming from the computer.Additionally, in the part of the article that did not make the excerpt presented here, there is data that shows only an 8-10% reduction in temperature on the bottom of the Laptop Desk with respect to the laptop itself. Given this modest decrease, even in their best case scenario, it is unlikely that the device would help alleviate the problem of elevated scrotum temperatures associated with laptop use. d) Based on the information in the two articles, do you think it was appropriate to include theinformation about the Laptop Desk in the second article? Why or why not? It was inappropriate to include the information about the Laptop Desk in the second article. First, as discussed in part a, the author of the article exaggerates the conclusions of the study to make the link to possible fertilityproblems seem more definite than it is so far. Second, the author deceptively uses only the first half of the quote by Dr. Sheynkin “It’s possible that external protective devices could help,” but leaves out qualification “somewhat” and the part of the quote that talks about the need to first determine their protective effect in a clinical trial. He uses the quote as the jumping off point to advertise the Laptop Desk, even though it is has never been clinically tested to illustrate its effectiveness as a means of reducing elevating scrotum temperatures with laptop use. 3Question 2 Hemoglobin is the protein complex that carries oxygen around our bodies and distributes it to the organs and tissues. Sickle cell anemia is a disease which results from the presence of abnormalhemoglobin (HbS) in the red blood cells. In order to have the disease a person needs to have only HbS hemoglobin. Wild-type hemoglobin (HbA) is composed of 2 α and 2 β subunits. The α and β polypeptides are approximately the same length, and are very similar in their primary structure. a) If you run HbA on a denaturing gel, how many bands are you likely to see? Why? You are most likely to only see one band, since on the denaturing gel the small difference in size between the α and β subunits (4 amino acids) is unlikely to be detected. However, it is possible to use a set of conditions that would differentiate between bands 4 amino acids apart. If these conditions are used, you will see two bands. When mutant HbS and wild-type HbA hemoglobin molecules are analyzed on a denaturing gel, they produce identical patterns. b) What is the likely defect in the HbS? Why? If the patterns are identical, then the problem with the mutant protein is not due to the loss or gain of a major portion of a protein. Therefore, the likely defect in HbS is an amino acid substitution.At low concentrations of O2 HbS forms rigid rod-like complexes in the cell. These complexes deform the red blood cells from saucer shape to sickle-like shape. These rigid, sickle-like cells can get stuck inthe small blood vessels and cause damage. The β-subunit of HbS has amino acid valine in position 6, where the wild-type molecule has aglutamic acid. • At normal oxygen
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