2nd midterm possible exam questions

2nd midterm possible exam questions - PMB 40: Possible...

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PMB 40: Possible questions for second midterm, Spring 2011. 1. Charles Darwin did a very simple experiment to show that there was “something” at the tip of the coleoptile (the protective sheath covering the emerging shoot of monocots) that caused it to bend towards light. Describe this simple experiment. When he covered the tip of the plant with tinfoil, there was no response. However, when he covered the rest of the plant with sand and left the tip exposed, the plant bent towards the light. He concluded that there must be something at the tip. 2. Describe the experiment and the bioassay used to demonstrate the direction of auxin movement. Bioassay is the testing of a biological system for a response to a chemical substance. Fritz Went cut off the tip of a plant and onto an agar block. When the material (later identified as auxin) diffused into the agar block, he placed the block back on the plant. Compared to the control agar block, the auxin-infused agar block incited growth towards light. Bioassay helped chemically identified auxin. 3. Define “apical dominance”. What happens when the apex of a plant is removed? Why causes the plant to respond this way? Apical dominance is the consequence of the polar transport of auxin from the top to the bottom; the growth of lateral buds/shoots is prevented. When the apex of a plant is removed, bud/shoot growth increases because there will be more cytokinin than auxin. 4. Explain the molecular bases for polar auxin transport. Two proteins help transport auxin. Auxin is taken up by an influx carrier protein, and exported by an efflux carrier protein. There are more efflux proteins so that the auxin can be immediately transported out, and the efflux proteins are located at the bottom of a cell in order to transport the auxin downwards. 5. Say you have a piece of plant tissue. Place it on 3 different ratios of auxin to cytokinin. Make up some auxin to cytokinin ratios and then say what the plant tissue looks like when grown on these different ratios of auxin and cytokinin. Auxin (3 mg) & cytokinin (3 mg) both high results in a callus cell. Auxin high (3 mg) & cytokinin low (1 mg) results in more roots. Auxin low (1 mg) & cytokinin high (3 mg) results in more shoots. 6. Compare the functions of abscisic acid versus gibberllic acid. GA promotes stem growth, ABA promotes bed and seed dormancy. 7. What 2 factors were responsible for the “Green Revolution” in wheat?
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This note was uploaded on 04/29/2011 for the course MATH 16B taught by Professor Sarason during the Spring '06 term at University of California, Berkeley.

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2nd midterm possible exam questions - PMB 40: Possible...

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