forensic biology exam 1

tips for sample collection

avoid contamination by using PPE, tweezers, etc

items are packaged individually, sealed, & clearly marked

chain of custody

commons samples that can be from the suspect, victim, and/or witness

blood

hair

semen 

saliva

body tissue

buccal/cheek swab

teeth and bone

urine and feces

skin cells touch DNA

not every sample source is BLANK

good for DNA testing

collection methods

don’t contaminate with your own DNA

wear clean gloves for each item

package items separately

air dry liquid samples before sealing bags

common collections methods/techniques

collection the whole item (weapons)

cutting (cutting up piece of bloody carpet)

double swabbing technique

tape life (fingerprints)

DNA is best preserved in BLANK

cool dry storage conditions

most common storage methods

bloodstain cards (FTA cards)

FTA cards are made to BLANK

lyse open cells and preserve DNA for long-term room temp storage

serologists are responsible for

documenting type of evidence, quantity & packaging

providing a description of the evidence for the case file

keep detail notes of testing (type of testing) and outcomes

proving a written report of testing and outcomes

planning the examination of evidence depends on BLANK

details of the incident

time since incident

when documenting the packaging you need to BLANK

notice the packaging and its condition

check to see if the chain of custody been maintained

when opening the packaging you need to BLANK

not open where previously sealed

cut a new slit and reseal when done

forensic serology

the detection, classification and study of various body fluids and their relationship to a crime scene

forensic serology includes

screening of items plus presumptive and confirmatory tests

presumptive tests (preliminary tests)

establish the possibility of a specific bodily fluid being present BUT does not conclusively prove the presence of a specific substance

pros of presumptive testing

cheaper & quicker

can be done at the crime

establishes what next steps should be

narrows possibilities

can be used on larger areas

can locate possible evidence not visible to naked eye

cons of presumptive tests

risk of false positives

may be overly sensitive

confirmatory tests

conclusively identify biological material

pros of confirmatory tests

conclusively identifies a substance

smaller risk of false positives & negatives

cons of confirmatory tests

may be more expensive

requires additional equipment

take longer

positives of using serology

links suspects and victims to each other and/or the scene

include or exclude potential suspects or victims

establish crime scenes

identify weapons

corroborate case circumstances

analysts in the forensic serology unit

screen the evidence for the presence of biological material

document the physical evidence

select an evidence processing scheme

collect and preserve biological samples for further analysis

alternative light source (ALS) assists in screening of evidence items because

some strains will fluoresce under different wavelegnths of visible light

parts of blood

serum (55%)

cellular (45%)

serum includes

90% water

inorganic ions

serum proteins nutrients

waste products of metabolism

respiratory gases

hormones

cellular includes

erythrocytes (RBC)

thrombocytes (platelets)

leukocytes (WBC)

erythrocytes (RBC)

5-6 million cells per µl

hemoglobin, peroxidase enzyme

no DNA

thrombocytes (platelets)

150,000-400,00 cells per µl

clotting

no DNA

leukocytes (WBC)

5,000-10,000 cells per µl

fight infection

contains DNA

blood is six times more BLANK than water to increase clotting

viscous

presumptive tests for blood

kastle meyer (KM)

TMB & LMG test

luminol

kastle meyer test uses BLANK to detect the presence of hemoglobin

phenolphthalein

how does kastle meyer test work

hemoglobin catalyzes the oxidation of phenolphtalin into into phenolphthalein by H2O2

kastle meyer gives off a BLANK

bright pink color

problems with kastle meyer

possible false positives

can’t distinguish between human and animal blood

tetramethylbenzidine (TMB) test

blue/green color change

Hemastix

leucomalachite green (LMG)

green color change

luminol is normally BLANK

sprayed on suspected surfaces and produces a blue fluorescence seen under UV light

luminol detects BLANK

iron in hemoglobin

luminol is useful when

search is large

surfaces are dark

blood isn’t visible

if someone tried to clean the blood

problems with luminol

only presumptive

false positives

DNA can be diluted

harder to get DNA profile

blood pattern analysis ruined

DNA is NOT a BLANK

confirmatory test for blood

confirmatory tests for blood

RSID Blood

HemaTrace

RSID blood detects the presence of BLANK

human glycophorin A

HemaTrace targets BLANK

human hemoglobin

Takayama test uses BLANK

ferrous iron from hemoglobin which reacts with pyridine to produce red feathery crystals

problems with Takayama test

requires large sample

not human specific

difficult to obtain accurate results with old blood stains

whole semen is a BLANK

suspension of cells and spermatozoa in a seminal plasma

seminal plasma contains BLANK

high levels of the enzyme phosphatase and phosphorylcholine

abnormalities in semen

aspermia

azoospermia

oligozoospermia

necrozoospermia

aspermia

no semen is ejaculated

azoospermia

no spermatozoa are present in an ejaculate

oligozoospermia

low numbers of spermatozoa are present in an ejaculate

necrozoospermia

condition in which all spermatozoa present in an ejaculate are dead

presumptive tests for semen

AP test

PSA or P30

semen contains high amounts of the enzyme BLANK

acid phosphatase (AP)

how does the AP test work

alpha Naphthyl acid phosphate and Brentamine fast blue reacts with AP and produces a deep purple color

problems with AP

age of stain can impact the test

false positives

how does prostate specific antigen (PSA or P30) test work

uses antigen/antibody test that detects P30, which is a protein in seminal fluid

problem with PSA or P30

small amounts can be found in

• fecal matter

• sweat

• male and female urine

• breast milk

confirmatory tests for sperm

microscropy

sperm hy-liter

RSID sperm

microscopy is the best way to confirm presence of BLANK

sperm

Christmas tree stain

Picroindigocarmine stains neck and tail green/blue

Nuclear fast red stains sperm heads red and tips of heads pink

sperm hy-liter

specific to human sperm

stains heads (targets DNA)

RSID semen test identifies the presence of BLANK

human seminogelin

must be aware of BLANK with RSID semen

high dose hook effect

high dose hook effect

a weak positive or false negative result is observed when very high levels of the target are present in the tested sample

Y-screening is an increasingly used method that looks specifically at the BLANK

DNA of a male

BLANK is a substance produced in the mouths of humans and most animals

saliva

main purpose of saliva is to BLANK

help breakdown food

saliva is BLANK

98% water

saliva contains

electrolytes

mucus

enzymes

nucleated epithelial cells (NECs)

electrolytes

sodium, potassium, calcium, magnesium, chloride, phosphate

mucus

mucopolysaccharides and glycoproteins

enzymes

alpha-amylase, lysozyme, lipase

nucleated epithelial cells (NECs)

nuclear DNA

BLANK is the most common test to identify saliva

Phadebas test

Phadebas test is BLANK

confirmatory for alpha-amylase but is presumptive for saliva

how does Phadebas test work

alpha-amylase hydrolyses a starch polymer, which makes it water soluble and release blue dye into paper

steps for Phadebas test

1. place item on clean, flat surface

2. dampen Phadebas paper with water and cover testing area with paper with reagent side down

3. trace outline of testing area on Phadebas paper

4. cover Phadebas paper with clean glass board and weigh down arrangement

5. start timer and observe the test during 40 minutes, record time of positive reaction

test tube test for Phadebas is BLANK

destructive

problem with Phadebas test

amylase is present in other body fluids but in a lower concentration (ex. vaginal secretions, feces, human breast milk)

amylase is produced by pancreas (blood and urine)

BLANK is confirmatory and specific to human salivary amylase

RSID saliva test

RSID saliva test has BLANK

NO high dose hook effect

BLANK is not encountered often and contains very little DNA

urine

BLANK is the closest confirmatory test for urine (not entirely)

RSID urine

RSID urine detects BLANK

presence of Tamm-Honsfall (TMP) glycoprotein

RSID urine is not BLANK

human specific

uncommon sample types

feces

sweat

vaginal secretions

steps for DNA profiling

1. extraction

2. quantification

3. amplification

4. separation

5. analysis

sources of DNA

tooth

bone

blood

hair

semen

saliva

hair

aims of DNA extraction

1. disrupt cell/tissue

2. inactivate DNA & RNA degrading enzymes (DNases, RNases)

3. denature proteins & nucleoprotein complexes

4. separate nucleic acids from other cellular components

5. take steps to maximize the quantity and quality of recovered DNA

PCR inhibitors

any compound that binds to the Taq DNA polymerase enzyme and prevents its function during PCR amplification

PCR inhibitors should be removed during DNA extraction, if not they would BLANK

compromise the DNA

PCR inhibitor from blood

heme

PCR inhibitor from hair and tissue

melanin

PCR inhibitor from urine

urea

PCR inhibitor from feces

polysaccharides and bile salts

PCR inhibitor from bone

calcium ions

PCR inhibitor from soil, plant material

humic acid