Lab Practical 2

Lab Practical 2 - Suggested answers for practical exam 2...

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Suggested answers for practical exam 2 (13140) 1. (put the comb) closer to the black electrode [because DNA is negatively charged, and you would like to use most length of the gel] (If put in the center, you get partial because you might be thinking of the dye electrophoresis we did in the lab; if you put the comb close to red electrode, you cannot get points for this one). 2. (DNA loading dyes) Crystal violet, Malachite Green HCl. (Because they go opposite direction with DNA). 3. (restriction enzyme) a) Lane III b) Lane II c) Lane IV 4. (why are there less bands than expected in the gel) (1) We added 10uL mixed dye into one well, while for all the other single dyes we added 10uL for each single well. No matter how the 5 dyes are mixed in 10uL, any band coming out of the electrophoresis is going to contain much less dye than the lanes with only one dye. (2) Some of the bands might be combined or mixed, since dyes produce wide bands. 5 . (left/right-handed helix) a) B-DNA is right-handed. b) left-handed. c) left-handed. 6. (Fermentation tube) a) Fermentation tube/flask. b) Parafilming prevents new oxygen goes into the tube. Oxygen can suppress fermentation, instead of starting fermentation right away, yeast carries on respiration till oxygen level dropped to some level, then enters fermentation. 7. (DPIP's absorbance curve) a) A curve that is lowest and flat at about 480nm where chlorophyll b has its absorbance peak, since chlorophyll b absorbs blue/purple light and is most efficient under blue light, while DPIP absorbs everything but blue/purple. The curve should peak at 600nm , where you measured the absorbance. Strictly speaking you need to satisfy both to get the curve right, but in grading this, as long as you got one out of two you get points. b) a curve that is flat and low at least in visible light range (400-700nm), I have no idea how it
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Lab Practical 2 - Suggested answers for practical exam 2...

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