2. DNA
• DNA has been called the “ultimate identifier”
• Identify information from every cell in the body in a
digital form
• Not yet fully automated, not fast and expensive
• Theoretical limitation: Identical twins have the same
DNA
• Privacy issue – DNA contains information about race,
paternity, and medical conditions for certain disease
3. Physical Structure (cont’d)
• Chains are anti-parallel (i.e in opposite
directions)
• Diameter and periodicity are consistent
– 2.0 nm
– 10 bases/ turn
– 3.4 nm/ turn
• Width consistent because of
pyrimidine/purine pairing
5. Comparison Chart
DNA Conventional Biometrics
Requires an actual
physical sample
Uses an impression, image, or
recording
Not done in real-time; not
all stages of comparison
are automated
Done in real-time; “lights-out”
automated process
Does a comparison of
actual samples
Uses templates or feature extraction
6. Reference …TTCACCAACATGCCCACA…
F T N M P T
Patient …TTCACCAACAGGCCCACA…
F T N R P T
…TTCACCAACAGGCCCACA…
Extract DNA from Cells.
Sequence DNA.
Compare Patient
DNA Sequence to
Reference Sequence.
Search Database to
Determine if Patient
Mutation is Associated
with Disease.
Patient Sample: Blood or
Saliva.
Inside the Gene Machine:
How Information from DNA is Acquired and Used for Genetic Testing
7. DNA & Genes
• DNA is where the genetic information is stored
• Gene - The basic unit of heredity
– There are genes for characteristics i.e. a gene for blond hair etc
• Genes contain the information as a sequence of nucleotides
• Genes are abstract concepts – like longitude and latitudes
in the sense that you cannot see them separately
• Genes are made up of nucleotides
M.Alroy Mascrenghe 7
8. Nucleotides
• Nucleotides are the unit structure of
nucleic acids.
• Nucleotides composed of 3
components:
– Nitrogenous base (A, C, G, T or U)
– Pentose sugar
– Phosphate
– G - C
– A - T
9. Advantages to Double Helix
• Stability---protects bases from attack by H2O
soluble compounds and H2O itself.
• Provides easy mechanism for replication
10. Chromosomes
• DNA strings make chromosomes
• Analogy
– Letters - nt
– Sentences – genes
– Individual volumes of Britannica encyclopedia –
chromosomes
– All voles together - Genome
So in triplet codes – codon – protein information is carried
The codons that do not correspond to a protein are stop
codons – UAA, UAG, UGA
M.Alroy Mascrenghe 10
