Blood & DNA Evidence
Which blood component contains the nuclear DNA used for forensic genetic profiling?
White blood cells
What are the three main layers of the hair shaft, from outside to inside?
Cuticle, cortex, medulla
Which plastic has resin identification code #1 and is commonly used for water bottles?
PET/PETE (Polyethylene Terephthalate)
In paper chromatography, what is the mobile phase?
The liquid solvent, such as water or alcohol
An unknown liquid has a pH of 9 or higher and a pungent odor. What is it most likely to be?
Ammonia
A presumptive Kastle-Meyer test produces an immediate bright pink color. What does this indicate?
The sample may contain blood.
Which hair layer contains melanin, the pigment responsible for hair color?
Cortex
Which plastic has a branched polymer structure and is commonly used for bread bags and trash bags?
LDPE (Low-Density Polyethylene)
Why should the starting baseline be drawn with pencil instead of pen?
Pen ink can dissolve and run with the solvent.
Two acidic liquids have pH values of 2 and 3. One smells sour, while the other has a citrus odor. Identify both.
Vinegar (pH 2) and lemon juice (pH 3)
A blood sample agglutinates with anti-A and anti-Rh serum, but not anti-B serum. What is its blood type?
A+
A fingerprint has exactly one delta, and its ridges enter and exit from the same side. What pattern is it?
Loop
An unknown plastic is chemically resistant, commonly used in pipes and window frames, and can release toxic substances when burned. Identify it.
PVC (Polyvinyl Chloride)
A dye travels 4 cm while the solvent front travels 8 cm. Calculate its Rf value.
0.50
An unknown white powder is insoluble in water and turns iodine solution deep blue-black. Name the two possible substances.
Cornstarch and flour
What is the difference between the area of convergence and the area of origin in bloodstain analysis?
Convergence is a 2D intersection; origin is the 3D location from which the blood came.
A soil sample feels sticky, drains water very slowly, and forms a long ribbon when wet. What type of soil is it?
Clay
An unknown plastic floats in water (density 1.00 g/cm³) but sinks in a liquid with a density of 0.94 g/cm³. Which polyethylene type best matches it?
HDPE (High-Density Polyethylene)
Two pigments have Rf values of 0.25 and 0.80. Which has greater affinity for the paper?
The pigment with Rf = 0.25
Two white powders both have a pH of approximately 9 when dissolved in water. One fizzes with acid, while the other does not. Identify both.
Baking soda (fizzes) and sodium acetate (does not)
A bloodstain has a width of 3 mm and a length of 6 mm. Using sin(θ) = width/length, what is its angle of impact?
30°
Investigators find a hair shaft without its root. According to the presentation, why is this a limitation for DNA testing?
The root must be present for the DNA testing described in the slides.
A plastic is flexible, fatigue-resistant, has a density around 0.90–0.91 g/cm³, and is used in food containers. What is it?
Polypropylene (PP)
Two ink samples produce identical colors but different Rf values under identical conditions. Can they be considered a chromatographic match? Explain.
No. Both the color patterns and Rf values must match.
An unknown white powder is insoluble in water and fizzes when acid is added. Which calcium-based substance is it?
Calcium carbonate