exam_2_key - Name _ BIOLOGY 325H Genetics Spring 2008 Exam...

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Name ___________________ 1 BIOLOGY 325H Genetics Spring 2008 Exam 2 Before you do anything else , please: check to make certain that your copy of the exam is complete, i.e. 6 pages. print your name legibly in the space provided at the top of every page. _______________________________________________________ 1. [20 pts] A. What are the two major features shared by both mitochondria and chloroplasts that suggest that they evolved through endosymbiosis? These are the only organelles surrounded by a complete double cell membrane. These are the only organelles other than the nucleus with their own genome. B. In the case of chloroplasts, what modern bacterium is likely a descendant of the same lineage that became a chloroplast, and give two reasons we think this is likely. Cyanobacteria. There are several reasons we think chloroplasts come from the cyanobacterial line but here are the two that I thought most likely given what we talked about in class: (1) cyanobacteria are photosynthetic and use some pigments for light harvesting that are similar to modern chlorophyll a, (2) cyanobacteria are found in modern stromatolites and similar fossil bacteria are seen in fossil stromatolites that are over 2 billion years old. C. When the first eukaryotic cell engulfed the bacterium (without digesting it) that eventually became mitochondria, what selective advantage did the protomitochondrion provide to the eukaryotic cell? What change to the environment, brought about by the waste product of another bacterium, had to occur before the mitochondrion could be advantageous? The protomitochondrion significantly increased the efficiency of cellular respiration allowing an additional 36 ATP (maximally) to be produced from a molecule of glucose. Because mitochondria have oxidative respiration, O2 had to become common in the environment, due to photosynthesis, before the mitochondria could be a benefit to the primitive eukaryotic cells.
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Name ___________________ 2 2. [15 pts] For a human being at sea level, the P O2 in the plasma of oxygenated blood is 100 mm Hg. Answer the questions below based on the O 2 :hemoglobin binding curve at the right. A.
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exam_2_key - Name _ BIOLOGY 325H Genetics Spring 2008 Exam...

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