Solution Name: set PHYSIOLOGY 42-202 Quiz 5 21 February 2011 IMPORTANT: READ THE QUESTION CAREFULLY BEFORE YOU ANSWER. Please write your name on the back of the quiz in the top left hand corner (2 points) 1. Is cancer contagious (justify your answer)? And, explain the interrelationship between cancer and mutation using retinoblastoma (a familial form of cancer) as your example. It is not contagious because cancer represents somatic mutations not genomic mutations. In retinoblastoma, if both alleles for the Rb gene are knocked out this represents the first hit mutation but not cancer directly. Additional mutations must occur for a cancer to result. The loss of Rb though is critical because the gene codes for a critical gate keeper in the cell cycle that helps to protect from cells with damaged/mutated DNA from surviving. One additional or more subsequent mutations are required for cancer progression from benign to metastasis forms. (note- to get a correct answer for the second part...basically outline multi-hit mutations) (4 pts) 2. Please identify ONLY 8 of the structures indicated. (You get no extra credit for identifying more than 8)
I band Part of a skeletal muscle fiber (cell) Z disc A band H zone M line Sarcolemmma Triad Myofibril Mitochondria Myofibrils Tubules of the sarcoplasmic reticulum Terminal Sarcolemma cisterna of the sarcoplasmic reticulum T tubule I band Z disc
(4 pts) 3. Now that you have successfully completed question 2 above, in respect to the sliding filament model, what happens to the sarcomere during a contraction? What aspects of the sarcomere change in length and which do not and why? -During contraction of the sarcomere, the actin or thin filaments slide along the -myosin or thick filaments, thus it gets shorter. -The A band does not change because neither the actin or myosin filament length changes. -The I band gets shorter because it is the represents the distance between two neighboring actin filaments between two sarcomeres. When the actin filaments slide along the myosin filaments the actin filaments get closer because of their staggered placement. -The H zone gets shorter because it is the distance between two actin filaments in the same plan within a sarcomere, thus when the actin filaments slide toward the middle of the sarcomere they come closer to one another. filaments get closer because of their staggered placement. -The H zone gets shorter because it is the distance between two actin filaments in the same plan within a sarcomere, thus when the actin filaments slide toward the middle of the sarcomere they come closer to one another.