DNA FINGERPRINTING

Deoxyribonucleic acid (DNA) in the Cell

cell nucleus

chromosome

Double stranded DNA molecule

Double helix

The chemical structure of everyone's DNA is the same. The only difference between people (or any animal) is the order of the base pairs.

•Some regions- no genetic information -JUNK DNAvary enormously•short sequence of DNA has been repeated a number of times-Variable number tandem repeats –VNTR/STR

•DNA Fingerprinting –used to distinguish individuals, method of identification that compares fragments of DNA called DNA typing.

DNA Fingerprinting-Definition

Genetic continuity

Brief History of DNA TypingBrief History of DNA Typing

1954 - Watson & Crick described the structure of DNA (Nobel Prize)

1984- DNA fingerprinting developed by Alec Jeffreys

1985 - Mullis developed protocol for polymerase chain reaction (PCR) (Nobel Prize)

Sources of DNA

STEPS IN DNA PROFILING

Extraction of DNA

DNA amplification by PCR

Electrophoresis on Agarose gels

Genetic analyser

Analysis and interpretation of results

DNA is the choice for individual identification

Discrimination/Distinguishing

No two people except identical twins (monozygotic) will share the same genetic blueprint. Identical twins are essentially clones.

Genetic Continuity

The DNA found at birth in each of our cells will contain the same genetic blueprint that will be present in our cells at death. In addition genetic continuity extends across generations allowing family members to be identified through similar DNA genotypes.

Sensitivity

A few drops of blood, a buccal swab or a small semen stain will generally contain ample amounts of DNA for analysis.

Stability

The DNA molecule resembles a twisted ladder comprising three chemical components to form a phosphate-sugar backbone joined by rungs of organic bases (adenine, guanine, cytosine and thymine).

Real world applications

Which one matches?Food identification

Crime scene Human remains

Human relatedness

Anthropology studiesD

isease-causing organisms

Paternity

Monitoring transplants

Animal relatedness

Most Important cases solved by this technology

Fast track DNA analysis confirms the Saddam’s identity

Rajiv Gandhi assassination case –Elusive criminals like Sivarasan and 'Dhanu', have been tracked by DNA fingerprinting technique

Naina Sahni 'tandoor' murder, proved that the half charred remains were indeed of Naina

DNA is a powerful tool,

both for conviction and

EXONERATION of

suspects.

We can use –DNA Fingerprinting

•DNA identifications after the 9/11 World Trade Center attack -this technique facilitated the identification of 1594 of the 2749 victims)

• Tsunami disaster – 2004

Size Mother Baby FatherHypothetical gel patternfor microsatellite heterozygousfor all individuals.

DNA fingerprint of Typical paternity case