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Forensic Science
The use of science to investigate crime and present unbiased scientific evidence in court.
Chain of Custody
The process of maintaining secure and accountable possession of evidence from when it is first encountered until it appears in court.
Frye Standard
A legal standard that requires scientific evidence to be accepted by the scientific community before it can be admissible in court.
Daubert v Dow Pharmaceuticals
A case establishing that scientific evidence may be admissible if it has been previously used for scientific research and is a valid method for its intended purpose.
Comparison Analysis
Determining if evidence is the same as or similar to a known source.
Elimination Evidence
Evidence that is used to rule out individuals rather than identifying them.
Individual Evidence
Evidence that has a high probability of being linked to a specific individual, such as DNA.
Class Evidence
Evidence that can be associated with a group rather than a specific individual, such as shoe prints.
Expert Witness
A specialist called to interpret results and draw conclusions in court regarding scientific evidence.
Biologist Role in Forensics
A forensic biologist analyzes DNA and bodily fluids to determine the type of blood and the possibility of DNA extraction.
Forensic Toxicologist
A forensic scientist who analyzes fluids and tissues for drugs or poisons, working in medical examiners’ offices.
Physical Evidence
Any substance or artifact that establishes or disproves a fact related to a crime.
PCR (Polymerase Chain Reaction)
A technique used to amplify DNA sequences through cycles of temperature changes.
Gel Electrophoresis
A method used to separate DNA fragments based on size during the analysis process.
STR (Short Tandem Repeat)
Short sequences of DNA that can be amplified by PCR and are less likely to degrade.
Forensic Anthropology
The study of human skeletal remains to determine various factors, such as age, gender, and cause of death.
Forensic Odontology
The application of dental science to legal cases, including identification of remains.
Forensics and the Law
Evidence must be analyzed and discussed according to legal standards to be admissible in court.
Ponderous of Evidence
The level of evidence needed to convict someone in a civil case.
What is the average adult human blood volume?
5 liters
What component is responsible for bloods red color?
hemoglobin
GIve me an example of an allele
ii, I^BI^B , i I^A
What is homozygous dominant B
I^B I^B
What compound is found in the majority of cells in blood
erythrocyes
if someone has AB- blood what can they receive?
They can get B- blood, A- blood or O- blood and AB-
If someone has B- blood, then what antibodies o they carry
the positive antibody(anti-Rh) and anti A
what information can be found from a blood splatter
who was or wasnt present, type of weapon, relative positions of the individuals involved in the crime, how close a gun was to the victim, how many blows were struck, action or motions of wounded
what type is a luminol test (spray)
presumptive
order of blood evidence investigation
test if its blood using kastle meyer test
obtain samples of blood from evidence to confirm its blood at lab
forensic biologists study blood splatter patterns from scene
blood samples from persons of interest are compared to blood from scene
forensic reports on the blood analysis are given to investigators.
what does higher voltage mean in gel electrophoresis
faster the DNA will fun through the gel matrix
where do you put the comb for making the gel?
negative side because DNA carries an overall negative charge, and it moves to the positive side
What makes PCR specific to single DNA region like a STR loci used in CODIS
primers
why might you not see a band in a lane of gel but you might in the other lanes?
no pcr amplification happened
samples were not properly loaded
what chemical activity happened in TLC when the sample moves up the paper?
capillary action
which blood test analysis involves emitting a blue light to small amounts of blood?
luminol
if loading dye is not added what happens
DNA cant sink into the well :(
why do we need to allow time for TLC
to get an accurate and true Rf value
smaller amplicons will be…
farther down the gel (moves faster)
what is the stationary phase in TLC
the silica gel coating
what is the mobile phase for TLC
the solvent
what does the ladder do in gel electrophoresis?
provides reference sizes of amplicons seen as bands
3 steps of PCR
denature, anneal, extend
From TLC samples are never ___(identitcal/match) but____(identitcal/match)
identical but match(similar)
types of confirmatory tests:
blood typing
crystal tests( takayama)
ouchterlony test
high performance liquid chromatography
guanine and thymine have how many bonds?
wrong they have no bonds its guanine and cytosine(not thymine) and they have 3 bonds
DNA replication steps
topoismerase
helicase that unwinds
single stand binding proteins to keep from twisting back together
primers adds the primers
sliding clamp holds polymerase III
(elongation) polymerase III adds complementary bases to the two single strands in 5’ - 3’
RNA primer is removed by exonuclease and
DNA polymerase 1 replaces primer with DNA
ligase seals
How to create a DNA profile simple steps
identify DNA source
extract DNA
ampligy DNA through PCR at various STR loci
RUn gel electrophoresis
analysis
interpret
electrophoresis data
what the flip is a CODIS
its a system by the FBI. they use the STRs from 13 loci STRS that are repetitive DNA sequences in noncoding regions and keep a log of them for different individuals.
deep sequencing
also called next-generation sequencing and it is when shotgun sequencing is implemented on a massive scale where 100s of millions of short reads can be made at the same time.
what is a major challenge in deep sequencing?
takes too long
What is sanger Sequencing?
sequencing method but the chain is terminated when the di-dNTP is added onto the growing seuqence because of the lock of the 3’ oxygen group
PCR v DNA replication
Unwind:
PCR: denatures the DNA to break apart using temperature
DNA: uses helicases to unwind DNA
Primers:
PCR- DNA primers
DNA-RNA primers
Polymerase:
PCR- Taq polymerase
What temperature is used for PCR so the DNA strands unwind
95 degrees
What temperature is used in PCR for the primers to lock on the complementary sequences
50 degrees
application of PCR
Detect harmful bacteria- PCR analyzes the DNA and finds the harmful contaminants that can be in water or food which they use to diagnose a patient
Paternity testing- Because DNA is given from the parents, PCR can amplify a series of genetic markers that can differ from person to person but you can see if a parent can match a child’s marker.
Identify viruses- PCR amplifies the genetic material and if it can not tell if a sample has infectious viruses then, the remnant can not hurt anyone.
these are only some
