DNA Profiling

Restriction enzyme

• DNA molecules are very long, often consisting of millions of base pairs

• Molecules are broken up into smaller fragments to study the structure of DNA by enzymes called restriction enzyme

• Don’t break up the DNA molecule randomly but “cut” it at particular sites

• The fragments cut by the restriction enzymes are called restriction fragments

• The fragments can be separated using gel electrophoresis and recombinant DNA

STR - Short Tandem Repeat

• Occurs when a pattern of TWO or more nucleotides are repeated and the repeated sequences are adjacent to each other.

• Pattern can range in length from 2 to 10 base

  pairs

• Typically in non-coding intron region

• Count how many repeats of a specific STR at a given locus can create unique genetic profile

STRs

• 90% or more of DNA does not carry nucleotide triplets that code for proteins

• Some of the non-coding regions (introns) consist of repeated sequences of nucleotides

• Currently over 10,000 published STR sequences in human genome

• Prevalent method for determining genetic profiles

  in forensic cases

• Analysis is performed by extracting nuclear DNA from cells of interest.

• DNA is amplified using PCR.

• Tested by gel electrophoresis or capillary

  electrophoresis.

STR - Applications

• Forensics

  • Crime

  • Mass disasters

  • Paternity testing

  • Military DNA “dog tag”

  • Convicted criminal DNA databases

• Bone marrow transplant follow up

  • Important for establishing graft reaction and disease relapse

Steps of PCR

1. Denaturing

   • DNA is heated to 92 degrees to break the DNA H bindings

2. Annealing

   • Cools down to 55 Degrees

   • Primate functions best at this temperature

3. Extension

   • Reheated to 72 degrees

   • Optimum temperature for nucleotide bases to be laid down

   • Taq polymerase