Forensics 6A

Question 1

Role of Micro-organisms

Answer 1

• To decompose dead organic matter into carbon molecules

- They secrete enzymes that decompose the material

Question 2

Estimating TOD

Answer 2

1 - Temperature - After death metabolic reactions slow and body temp falls, depending on how long after death body temp can tell TOD

2 - Rigor Mortis - 4-6hrs after death muscles are deprived of oxygen and lactic acid builds. Enzymes inhibited and no ATP produced to break Lactic acid

3 - Entomology - Insects colonise the body at different times after death. Insects life cycles can indicate TOD

4 - Decomposition - Bacteria and Enzymes decompose the body. Tissues break down, bloating occurs, tissues liquify, skeletal remains left, then no bones or fragments

5 - Succession - Insect species change over time on the body. Flies occur first, then larger insects and beetles

Question 3

DNA Profiling

Answer 3

A DNA profile is a fingerprint of an organism.

Used to identify people and determine relationships

Question 4

PCR (Polymerase Chain Reaction)

Answer 4

• This amplifies the DNA sample
  1) Reaction mix: DNA sample, free nucleotides, primers and DNA polymerase
  2) Heat mix to 95 to break H bonds between DNA
  3) Cool to 50-60 so primers can bind to strands
  4) Heat to 72 so DNA polymerase lines free nucleotides to the template strand
  5) 2 new DNA strands made

Question 5

Gel Electrophoresis

Answer 5

• This separates the DNA.
  1) DNA is spliced using Restriction Enzymes and Ultraviolet dye added
  2) DNA placed into well with gel and buffer solution
  3) Electrical current is passed
  4) Short DNA fragments travel further