Forensic biology

Forensic biology from the salters-nuffield sylabus.

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  • Created by: Saf
  • Created on: 11-04-09 15:32

Fingerprints

  • Are unique to the individual and remain unchanged over a lifetime
  • Formed by folds & ridges of epidermal layer of skin
  • Impressions of fingerprints are left as deposits of oil (sebum) and sweat

Analysing Fingerprints - Fingerprints must be 'developed' to be seen, this is done by:

  • Fine aluminium powder - attaches to residue
  • Ninhydrin - reacts with amino acids to produce a purple coloured impression

Positions of branching points, ridge endings, and inclusions are used for identification, for a fingerprint match there must be at least 16 matching points

Uses:

  • Identification of dead people (providing there is something to match it to)
  • Identification of Criminals at crime scenes
  • Security issues providing unique access

Henry Classifications of finger prints:

  • Arch
  • Tented arch
  • Whorl
  • Loop
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Dental records

If bodies are found in fires, are discovered after a very long period of time or have been damaged in such away that it makes other means of identification very difficult, dental records are the best means of identification.

Teeth and fillings decay slowly and are more resistant to burning than skin and muscle.

A forensic dentist makes a chart of teeth, including fillings dental work and any missing teeth, this can then be compared with dental work of missing persons etc. They can also look at the development of teeth to give an estimate of age of the person.

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DNA fingerprinting

  • Also known as DNA profiling
  • DNA is unique to individuals, excluding identical twins
  • Most DNA within a nucleus does not code for proteins (junk DNA)
  • The non-coding blocks are called introns and are inherited like a gene
  • Within introns, short DNA sequences are repeated many times, these sequences are known as mini or micro-stallites depending on the number of base pair repeated, they are unique to individuals.
  • Mini-satellites - 20-50 base pairs repeated from 50 to several hundred times
  • Micro-satellites - 2-4 base pairs repeated between 5and 15 times

Uses:

  • Criminal/ victim identification
  • Paternity cases
  • Security recognition
  • Determine evolutionary relationships

How is it anaylsed?

1) DNA is obtained e.g. white blood cell or hair folicle

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