DNA Fingerprinting
Variation in Human DNA
Of 3 billion nucleotides in human DNA more than 99% are identical
Of 1% that are different significant amount of code variations
RFLPs
For every 100 nucleotides inherited there is one site of variation, or polymorphism
These DNA polymorphisms change the length of strands cut by restriction enzymes
Fragments: restriction fragment length polymorphisms (RFLPs)
RFLP ANIMATION http://highered.mcgraw-hill.
com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120078/bio20.swf::Restriction Fragment Length Polymorphisms
Short Tandem Repeats
Most DNA in a chromosome is not used to code for genes
More likely to find differences in these regions which do not seem to be essential to an organism’s development
Regions contain sequences that repeat many times
(e.g. GTCAGTCAGTCAGTCA)
What can STRs Tell Us?
Link Between RFLPs and DNA Fingerprinting
Difference in fragments leads to a DNA Fingerprint
Scientists have identified more than 3000 RFLPs in the human genome
Distinct RFLP patterns can be used: to trace family relationships, to track genetic disorders, in forensics, understand more about endangered species
Accuracy of DNA Fingerprinting
Accurate to within 1 in 1 billion
Gel Electrophoresis Review:Agarose Gel
Agarose: extracted from seaweed
HeatedMeltsSolidifies and forms a matrix of microscopic pores
Agarose Concentration
Size of pores depends on the agarose concentration
The lower the agarose concentration, the larger the pore size
Usually use from 0.5% to 2%
Gel Separation
Charge: buffer, power supply, DNA
Size: cut into pieces by restriction enzymes, small pieces move easier through the pores
Loading the DNA
Loading Dye used to help visualize when
loading the gel
Used for tracking the progress of the gel
Does NOT bind to the DNA
Visualizing DNAVisible Light Stain
(Usually Blue)UV Light Stain
(Ethidum Bromide)