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215-Lab1A-Pipeting

# 215-Lab1A-Pipeting - Lab 1A Pipeting Lab 1A Pipeting and...

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Lab 1A– Pipeting 1A-1 Lab 1A: Pipeting and Measuring Concentrations of DNA I. Background: Length, Volume and Mass The Metric System was devised by French scientists in the late 18th century to replace the disorganized collection of units of measurement then in use. To obtain a standard of length, a quadrant of the earth (one-fourth of a circumference) was surveyed from Dunkirk to Barcelona along the meridian that passes through Paris. The distance from the pole to the equator was divided into ten million parts to constitute the meter. In other words, the Meter is 1/10 millionth the distance from the pole to the equator. You are not responsible for any of the above information and have our permission to immediately forget it! It is worthwhile, however, to know that the units of volume and mass were derived from the meter. For example, the standard metric unit of volume, the liter, is defined as the volume of one cubic decimeter (10 cm on all sides) . Likewise, the milliliter, is defined as the volume of one cubic centimeter. Imagine a cube that is 1 cm in length on all sides (smaller than a cube of sugar). This is a c ubic c entimeter (cc or cm 3 ) and holds exactly 1 ml of liquid. Recall that in medicine the cubic centimeter is still used as a unit of volume (for example: 0.5 cc of epinephrine). The metric unit of mass , the gram, is defined as the mass of 1 ml of water . This holds true for 4 o C temperature water, because the density of water, which is greatest at that temperature, has been designated to be 1.00 (1.00 gm/ml). Therefore, mass and volume can be independent assays for the accuracy of each other as long as you know the liquid’s density. For example, the manufacturers of graduated pipets and micropipettors (such as the Pipetman brand) calibrate their equipment by weighing a defined volume of water to determine if the mass is in agreement with the presumed volume. Metric System Units The table below describes the prefixes for metric units commonly used in molecular biology. Prefix Meaning Exponential Notation mega one million 10 6 kilo one thousand 10 3 milli one-thousandth 10 -3 micro one-millionth 10 -6 nano one-billionth 10 -9 pico one-trillionth 10 -12 Below are tables of commonly used molecular biology metric units for volume, mass and number of molecules.

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Lab 1A– Pipeting 1A-2 Volume Symbol Equivalent liter l milliliter ml 10 -3 l microliter μ l 10 -6 l Mass Symbol Equivalent gram g milligram mg 10 -3 g microgram μ g 10 -6 g Molecules Symbol Equivalent mole mol millimole mmol 10 -3 mol micromole μ mol 10 -6 mol nanomoe nmol 10 -9 mol picomole pmol 10 -12 mol Problem Set: In this lab you will be dealing with very small units of metric measurement, therefore it’s important that you know what these units mean and know how to convert units. Below are a few sample problems to test your knowledge of these units.
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