Investigating CSI – Background material Table of Contents I ...

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VI. AN IMPORTANT NOTE One should not “read” the result of the KM test after 30 seconds or so. This is because the KM reagent may begin to turn pink after this time as the result of oxygen in the ambient environment, and not because blood is present. VII. HOW DOES THIS TEST WORK? The diagram below helps illustrate what happens in the KM test. Follow along as I describe each part. 1.) Hydrogen peroxide: Look at the chemical formula and compare it with the chemical formulas for water and oxygen. Oxygen (elemental oxygen) typically comes as a pair of molecules (as it has in the peroxide), but something in our test breaks it up. What might that be? 2.) Heme: This is where we find peroxidase-like activity. This is what breaks up peroxides. Peroxides are toxic to animal tissue, and are decomposed by the heme in our blood. In this case, hydrogen peroxide is decomposed into two parts: water, and a free oxygen radical. 3.) Follow the O (the free radical). It's going to combine with the KM, our phenolphthalein color-indicator. Why? 4.) When the KM solution is initially prepared, it is boiled in a flask for several hours to help remove oxygen. (A little bit of zinc metal dust added to the solution 28
helps to bind oxygen as well.) When the solution turns colorless, that means the KM has had most of its oxygen removed, and is now "oxygen hungry". So... now we have the makings of a kind of love story: the KM is badly in want of oxygen, and there's a lonely oxygen radical floating around, un-spoken for... What do you suppose happens next? 5.) Pink color: This is the blushing that occurs when the oxygen radical "hooks up" with the KM reagent. The radical oxidizes the KM, and this oxidation causes the KM to turn pink. Source: http://www.geocities.com/a4n6degener8/kastle.htm 29
Page 1 and 2: Investigating CSI - Background mate
Page 3 and 4: convict the killer of Gill Dando wa
Page 5 and 6: A forensic scientists needs a honou
Page 7 and 8: lond, is also wearing Air Jordans w
Page 9 and 10: of unidentified remains with the pr
Page 11 and 12: Matching DNA Proving that a suspect
Page 13 and 14: Creating a DNA Profile: The Basics
Page 15 and 16: with thymine and guanine with cytos
Page 17 and 18: power is the combined analysis of a
Page 19 and 20: of DNA profile comparisons done by
Page 21 and 22: II. Tools and Techniques for DNA Fo
Page 23 and 24: p30 Test Unlike the presumptive aci
Page 25 and 26: Specificity refers to how many othe
Page 27: expected to occur when using your c
Page 31 and 32: chemical reaction, but in order to
Page 33 and 34: 2. Brauner, P.& Gallili, N., "A Con
Page 35 and 36: DNA Extraction Techniques Organic-b
Page 37 and 38: C. Quantification of DNA Southern B
Page 39 and 40: Southern Up Close In this simplifie
Page 41 and 42: 2. cDNA is denatured at more than 9
Page 43 and 44: SYBR-green SYBR green is another me
Page 45 and 46: Let's look at two people and the se
Page 47 and 48: at this locus and a different sized
Page 49 and 50: These loci are located on the same
Page 51 and 52: Short Tandem Repeat (STR) Analysis
Page 53 and 54: The other two PowerPlex16 groups of
Page 55 and 56: The Federal Bureau of Investigation
Page 57 and 58: eference sample from the standard s
Page 59 and 60: III. Interesting Cases Using DNA Ev
Page 61 and 62: me. But I was also lucky that when
Page 63 and 64: The tests indicated that the drops
Page 65 and 66: July 17, 1918. Czar Nicholas II, hi
Page 67 and 68: Guest list pared With the refusal o
Page 69 and 70: But only 18 of the states are hooke
Page 71: that to all felony offenses, as Ala

Investigating CSI – Background material Table of Contents I ...

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