FORENSICS

Cabanto, Ecat, Talampas, Vocal, Beleran, Mina

IV-Gluon

DNA fingerprinting: Overview

1984 - Sir Alec Jeffreys Also known as genetic fingerprinting or

DNA profilingWay of identifying an individual*Applications

ForensicsPaternity/Maternity tests

Why it is better than a fingerprint.

Fingerprints are easily obscuredDNA is in every cell of the body

Hair strandSkin follicleDrop of blood

How it works

99.9% of our genes are identicalThe remaining 0.1% is used to determine

the individualMicrosatellites

Short repetitive sequences that are highly variable in humans

Reflect individual genetic make-upA.k.a. Variable Number Tandem Repeats

(VNTR)

VNTR’s

short sequence in the introns of DNA that is repeated in a head-to-tail manner at a specific chromosomal locus

interspersed in genomeNumber of repeated units vary per humanLoci – VNTR’s

One VNTR – 17 bp, repeated 70 to 450 timesTotal: 1190 to 7650 base pairs

Southern hybridization

DNA with VNTR is cut with a restriction endonuclease

Size varies, creating RFLPs, or restriction fragment length polymorphisms

Analysis

Leads to a two-band pattern

Inherited from each parent

One band can occur if parental bands are identical/nearly the same

Basic Genetic Principles

Identity matching VNTR alleles should be the same if samples

are from the same individual.

Inheritance matchingHe or she could have VNTRs inherited from

his or her mother or father, or a combinationNever a VNTR either of his or her parents do

not have.

Other Uses

Personal IdentificationCasualtiesPaternity/Maternity testingFamily reunions yehey :D

Other Uses

Diagnosis of inherited disordersAlzheimer’s diseaseHuntington’s disease

Determining risks of having an affected child

Identify patterns associated with diseaseMay lead to cure for the disorder

Other Uses

Mapping genographyFind patterns of migrationTrace human species’ history

National Geographic SocietyStudy distinct trail left by humans since we left

AfricaUnderstand more about our background

In the Philippines

Case study: Ray de VillaJan. 9, 1995- Arrested for the rape of 13

yo nieceDNA testing was not done at that timeSole evidence was birth of a childCounter evidence – 76 yo suspect

suffered physical condition

Case Study

Victim did not report assault until confronted of pregnancy

Problem: Court did not allow paternity testing

Dr. Cora de Ungria of UP devised a way to be able to profile the child’s paternity

Both parties (child’s family and prison) refused for samples

“Spitting game” to get saliva from child and 4 other children

Blood from De Villa without assistance from prison staff

Results: genetic markers proved that De Villa could not have fathered any of the children

Parole was granted to De Villa after extensive legal action

Since then, Philippine Parliament has introduced DNA database legislation and the Supreme Court has issued rules for the admission of DNA profiling results in court

UP Diliman’s DNA analysis lab has also created a “rape kit”- Sexual Assault Investigation Kit for the Collection of Biological Samples

In the Philippines

Crop biologyanalysis of genetic diversity within breeding

populations in plantsDifferentiation between cultivarsIdentification of plants containing a gene of

interest

Issues

Privacy of suspectsStudies regarding human populationDNA evidence may place a person at a

crime scene, but it also does not necessarily mean that he or she committed the crime

DNA can still be tampered with, and still be used to frame people

Issues

Pattern narrows down a million people to around 2-10

Sometimes cannot identify individualHowever, if there are suspects in hand,

the match can be easily made