Forensic Biology Review

Vocabulary flashcards based on lecture notes covering forensic biology, serology, PCR, and cell membrane structure.

ABO Blood Type

Present on red blood cells

Allelic ladder

measure lengths of DNA fragments.

Gene

piece of DNA that codes for smt.

Allele

variant of a gene.

Mitochondrial DNA

Maternally inherited, circular DNA.

STR

Example: D5S818 

DNA 5th chromosome single copy location 818

 2 alleles per locci - could be Homozygous vs Heterozygous

Forensic Biology

The application of natural and applied sciences to investigate crimes.

forensic biologist Does

presumptive, confirmatory, extractions, PCR, USING objectivity & scientific inquiry

blood type

not useful, cheap

locards

every contact leaves a trace

unknown sample

dont know origin

known sample

know origin, from suspect/victim

NIST guidelines

wear gloves, change w/ new evi

unique IDs

diff origin, diff box

evidence

dry - scarp onto paper or add water n scrub

wet - pipette or swab

cut out?

chain of custody

list of ppl who have had possession of evi

needed for contamintion & integrity

for no tampering

serology

1) Identify what fluid to save money/time

blood type A

antigen A , antibodies B

bc antibody A smokes antigen A

• Genes you inherit from your parents.

• antigens on surface of red blood cells

• immune responses if incompatible blood types are mixed.

presumptive test

“it could be”

hemoglobin

iron gives red color

heme → oxy → methe (brown)

KM Test

2) add indicator - wait to see if regents work or smt other than blood (eliminates false positives)

3) peroxide

Release of O2 = pink = if hemoglobin and O2 present = blood

specificity

few things react

low false pos. rate (wont detect other things)

sensitivity

many things eract

high false pos. rate (detects tiny amounts)

RFLP

 Uses restriction enzymes , not pcr based

pros:

highly discrm.

cheaper

con:

slow

large amounts dna

VNTR

con = dont w/ voltage (warps), messy profiles or incomplete digest, ALOT of DNA, cant do saliva/fingerprints (unique contact evi)

PCR

amplify or copy DNA - Denature,anneal,extension. (three stages) - thermal cycler

1) template DNA or RNA

2) 2 primers (Attach to template strand and flag DNA polymeraset)

3) DNA poly (Finds primer sites & pulls nucleotides out of buffer)

4) DNTPs (Building blocks (A,T,G,C)

5) Buffer (holds everything togher)

PCR advanatges

small amounts of DNA

used w/ degraded

multiplexing (multiple targets used at same time = fast )

PCR disadvatnages

too sensitive = contamination amplify

inhibitor

suspect w/ mutation = no amplify

stochastic effects PCR

low DNA

allele dropout = false homozygosity

some alleles wont show up = preferential DNA