FRSC Quiz 4 (serology, dna, paint metal and soil)

What’s the most common type of paint that comes into the lab?

Automotive paint

Automotive paint layers

1. Electrocoat primer

2. Primer surfaces

3. Base coat/color coat

4. Clear coat

How is soil analysis useful

Helps create a link between a suspect and a crime or a crime scene and another location

Color, texture, and mineral composition are compared using microscopy, spectroscopy, and chemical analysis

Preliminary examinations

Visual and microscopic observation: examiners look for obvious foreign material and characteristics such as color/texture for clues on its origin

Laboratory examination

• particle size analysis

  • Sieve separates soil into dif grain ranges to determine particle size distribution

• Microscopic examination

  • Microscope used to analyze the mineral content, composition, and structure of soil particles

• Density gradient tests

  • Density gradient created in a. Liquid and soil sample is added to see how it separates into dif layers, revealing its density profile

Laboratory analysis

Chemical tests

Ignition and heat tests

Evidence

Serology

Scientific study/diagnostic examination of blood serum, especially in regards to the response of the immune system to pathogens or introduced substances

When was the first successful blood transfusion

1665 → bw dogs

What happens when a blood transfusion fails

Instant death ! Transfused blood will coagulate in the recipient

Blood def.

Mixture of cells, enzymes, proteins, and inorganic substances

What is the fluid portion of blood

• plasma

  • Primarily water and accounts for 50% of blood content

What are the solid material suspended in the plasma

Mostly cells,

Erythrocytes, leukocytes, and platelets

Erthyrocytes

Red blood cells

Leukocytes

White blood cells

Platelets

Cells that bind together when vessels are damaged

Antigens

Proteins on the surface of red blood cells that stimulate the body to produce antibodies and are responsible for blood typing

Antibodies

Proteins that destroy/inactivate a specific antigen

Type A Blood - what antibodies, antigens and compatible types

Anti B antibodies

A antigens on the surface

Compatible with type A and O

Type B Blood - what antibodies, antigens and compatible types

Anti A antibodies

B antigens on surface

Compatible with type B and O

Type AB Blood - what antibodies, antigens and compatible types

No antibodies

A and B antigens on the surface

Compatible with A, B, AB, and O (AB POS is UNIVERSAL RECIPIENT)

Type O Blood - what antibodies, antigens and compatible types

Anti A and Anti B antibodies

No antigens

Compatible with Type O (UNIVERSAL DONOR)

Blood clots

Form when protein Fibrin traps and entangles red/white blood cells, platelets and solids

What remains after blood clot is removed

Serum → yellowish liquid of plasma without fibrinogen

Rhesus factor/Rh factor

Inherited protein found on the surface of the red blood cells

• if ur blood type is pos, blood cells have Rh protein.

• If blood type is neg, then blood cells don’t have the protein

Immunoassay

Tests to measure the presence and/or concentration of analyze

Ex. Covid test and pregnancy tests

Analyte

Molecule detected by immunoassay

Polyclonal antibody

• cheap to produce

• Mixed population of antibodies

• May bind to dif. Areas of the target molecule

Monoclonal antibody

• expensive to produce

• Single antibody species

• Will only bind single specific site

• May only recognize a particular protein form

How are polyclonal antibodies made

Using different immune cells. They have the affinity for the same antigen but dif epitopes

How are monoclonal antibodies are made

using identical immune cells that are all clones of a specific parent cell

What’s the best way to detect/indicate presence of blood at a crime scene

Preliminary color test

Kastle-Meyer (phenolphthalein) Test

• based on the observation that blood hemoglobin possesses peroxidase-like activity

• Phenolphthalein reagent and hydrogen peroxide are mixed together and the hemoglobin causes the formation of a deep pink color

Not specific to blood, some vegetation will turn pink as well (potatoes and horseradish)

Peroxidase

Enzymes that accelerate the oxidation of several classes of organic compounds by peroxides

Luminol

Contains hydrogen peroxide, which combines with the iron in the blood to produce oxygen

Oxygen and luminol react and form a luminescent compound

Requires COMPLETE DARKNESS for max effectiveness

Blood, bleach, feces, urine, and horseradish, all trigger luminols chemiluminescence

Bluestar

Easier to mix and extremely sensitive to blood +doesnt require complete darkness for visualization

Does luminol or bluestar effect the sample?

No ! It doesn’t interfere with subsequent DNA testing which is important because evidence wont get destroyed before it gets to another discipline

Genes

unit of inheritance consisting of a DNA segment located on a chromosome

Chromosome

Threadlike structure of nucleic acids and protein found in the nucleus of most living cells carrying genetic information in the form of genes

How many chromosomes in human cells

46 total, 23 from mom/egg and 23 from dad/sperm

How many mL is normal ejaculate And how much spermatozoa in each mL

2.5-6 milliliters

100 mil spermatozoa in each mL

Acid phosphates

Enzyme secreted by phosphate gland

Concentration of this enzyme is 400x greater in seminal fluid than any other bodily fluid

What’s significant about spermatozoa

It’s only found in sperm, so it’s prescience can unequivocally identify sperm

Seminal fluid with no sperm can happen however if a person has had a vasectomy or if they have a really low sperm count

What nucleotides + pairs are in DNA

Adenine + Thymine

Guanine + Cytosine

Summarize DNA Replication

DNA double helix strand unravels

Double helix is recreated as nucleotides are added led according to complementary base pairing

Now u have two identical copies of DNA

How is DNA replication important in forensics

PCR → polymerase chain reaction

Small/broken bits of DNA found in evidence are copied in order to increase the sample size

Short tandem repeats

Areas on the chromosome that contain short repeating sequences within the DNA molecule

They’re basically just fillers that have no effect on outward appearance or genetic function

What was used before PCR

RFLP → restriction fragment length polymorphism

It was laborious and expensive so it was short lived