Question

26 to 35

Page ot2 17. Complete the fomula used to determine the DNA concentration OD atmX100 Dilution facton X- ngu 19. The precipitated DNA was spooled out with a 20. MSDS is the abbreviation of 21. In NFPA (National Fire Protection Association) ratings, the color of the diamond shapes tells the following: Blue for : Red for and Yellow for 22. In NFPA ratings, OX is Oxidizer-8 CORR Corrosive compound, whie w indicates 23. Name a Carcinogen or Mutagen or Hepatotoxin 24. In Scientific Notation, 8162 will be expressed 25. The Units of Mass, Length and Volume n Metric System are:-- & Short answer 26. How you will prepare 1 L volume of 1M NaOH (MW 40)? 27. While drawing up the liquid with a micropipette, will you push the plunger to 1t or ze stop? Why? 28. Define LDso or LCso. 29. Why did you use mechanical pipetting(micropipette) over mouth pipeting? 30. During centrifugation, why did you balance the centrifuge tubes? 1. In your 1et lab of micropipette calibration, why did you use the Weighing Boat? 32. While using the Electronic Balance, you "Tarred the weighing boat. What does it mean? 33. In DNA assay, why an UV spectrophotometer was used, instead of a Visible spectrophotometer? 34. What conclusion can you draw from the ODs of DNA samples at 260 nm (OD: 0.280) and at 280 nm OD: 0.140)? Why? 35. In your Lab Safety class, why were you asked to wear a lab coat and gloves during lab activities? page 2 of 2

Answer 1

26. Molarity = wt of solute / M.wt × 1 / volume in liter

Wt of solute = 1 × 40 × 1 / 1 = 40 g

So, 40 g of NaOH should be dissolved in 1 l water to make 1M Naoh solution.

27. Aspiration until the 1st stop ensures that we get the right volume into the pipette tip. If we dispense until the 1st stop, then we will notice some residual liquid in the tip. Thus we would have dispensed slightly lesser than what aspirated. However, dispensing all the way until the 2nd stop ensures that we dispense all the volume that aspirated.

28. LD50 is the amount of a toxic agent that is sufficient to kill 50 percent of a population of animals usually within a certain time called also median lethal dose.

29. By using mouth pipette, poisoning in a chemical laboratory or becoming infected in a clinical laboratory may occur. Micropipettes measure a much smaller volume, starting at 1 microliter, while pipettes generally start at 1 milliliter.