Foresics Unit biotechnology

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