Forensics 413 final

When is hair sent to DNA?

if hair has root or skin tag

when is hair sent to Trace

when hair is fragmented

Sexual hair

hair that grows during puberty (pubic, arm/leg, beard)

course, continuous texture

beard hair

course, double medulla, triangle cross section

asexual hair

scalp hair

Proximal

root/bulb, reaches hypodermis, nearest origin

Medial

shaft, located in the middle

Distal

tip, located farther from origin

Anagen

live hair in active growth phase (2-6 years), root is hook-shaped, has tag when forcibly removed

Categen

transition phase (1-2 weeks), root starts to shrivel up, looks “slimy”

Telogen

resting phase (2-4 months), dead hair, no skin tag or root sheath

keratinocytes

skin cells

eumelanin

black and brown hues

pheomelanin

red and yellow hues

Asian hair

coarse, dense medulla,, thick cuticle, no undulation, round cross section

African hair

moderate to fine (variation), dense pigment granules with prominent clumps, prevalent undulation, flat cross section

Caucasian hair

moderate, sparse but even pigment granules, uncommon undulation, oval cross section

straight hair texture

circular cross section

wavy/curly hair texture

ovoid cross section

Cuticle

outside layer

what kind of cuticle type is this?

coronal

What kind of cuticle type is this?

spinous

what kind of cuticle type is this?

imbricate

cortex

main body of hair shaft

cortical fusi

tiny air spaces (cavities) usually around root

medulla

dark innermost portion of hair shaft consisting of air

what animal has wineglass root shape?

deer

what animal has javelin root shape?

dog

what animal has frayed root shape?

cat

what animal has club root shape?

human

central dogma

DNA -→ RNA → proteins

transcription

The process of copying a segment of DNA into RNA for the purpose of gene expression

where does transcription occur?

nucleus

translation

mRNA is read and used to bind individual amino acids into polypeptide chains to create proteins in ribosomes

where does translation occur?

cytoplasm

nDNA

located in nucleus

mtDNA

located in mitochondria

usage of nDNA

blood, tissue/skin, hair (with root), fresh bones/teeth, body fluids (saliva, semen)

usage of mtDNA

skeletal remains, hair shaft, degraded low-levels of DNA

individualization

to associate evidence to a single source with a high degree of certainty

uses of forensic DNA

• Matches victim to the scene

• Paternity testing

• Cold cases

• Missing persons (using parents)

• Mass disasters/ human remains

• Military DNA

• Convicted felons databases

VNTR and RFLP

early DNA technology that showed long sequences of non-coding DNA that required a lot of high quality DNA

Exons

coding DNA

introns

non-coding dna

gel electrophoresis

uses restriction enzymes to recognize specific VNTR nucleotide sequences and cut the DNA at these locations to form restriction fragments

PCR purpose

amplify/multiply specific DNA segment

PCR steps

denaturation, annealing, extension

PCR - denaturation step

breaks hydrogen bonds between nucleotides to get single strands

PCR - annealing step

short DNA primers bind to complementary sequences of ssDNA templates

PCR - extension step

Taq polymerase adds nucleotides to 3’ end of primers and synthesizes new complementary DNA strand

STR - short tandem repeats

Regions of repeating DNA sequences have been identified (usually in non-coding region)

allele nomenclature (D5S818)

• D = DNA

• 5 = chromosome 5

• S= single copy sequence

  • Represents unique DNA segment 

  • Copy wont be found anywhere else

• 818 = order of discovery in which locus was identified

amount of loci/markers in CoDIS

22

first step of DNA analysis

extraction

extraction

Isolate DNA in sample from everything else

steps of extraction

• Lyse the cell nucleus from: 

  • Human biological specimen

  • Non-human (seeds, leaves)

  • Microbial specimen (anthrax)

• Separation of DNA from other cellular components

  • Proteins

  • Cellular debris and internal cellular structures

  • carbohydrates

what extraction method is used for blood spot samples

FTA card

what extraction method is used for degraded/micro samples (automated). Can process blood, saliva, swabs, bones, and teeth.

solid-phase extraction (STR)

chelex

used for buccal swabs

what extraction method is used for challenging samples and is uses chloroform and phenol

organic

what extraction method is used for complex mixtures that separates sperm cells from non-sperm cells

differential extraction

steps of central dogma

• Transcription

• Translation

• DNA packaging

• Replicating

second step of DNA analysis

quantification

Quantification

Determine the amount of DNA present in the extract so we can add appropriate amount of extract for amplification

qPCR

real-time PCR that amplifies and quantifies DNA in real-time, allowing for precise measurement

what is third step of DNA analysis?

amplification

what is used during amplification step?

PCR

what is fourth step of DNA analysis

seperation

separation

electropherograms, loci used to create a profile of peaks, basic reading of peaks.