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)