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DNA Profiling
Field Trip 411
Basics
• Nucleus contains 23 pairs of chromosomes.
• Each chromosome contains alleles or versions of traits (ex: eye color, hair color)
• Sequences of these alleles on each chromosome are polymorphic (many forms)
• Polymorphic sequences provide information on paternity, ID and genetic testing
Alec Jeffries
• First researcher to realize DNA polymorphisms can establish human identity.
• Discovered in 1984
Repeat Polymorphisms• One class of polymorphism results from repeated
copies of a DNA sequence that lie directly next to eachother
• Each sequence can have tens of different alleles• Highly heterozygous (1 allele from each parents)
Common Polymorphisms
STR• Short tandem repeats
VNTR• Variable number of
tandem repeats
Other Repeats
• Di and tri nucleotide repeats cause mutations found in Huntington disease, Alzheimer Disease and fragile X syndrome
FBI
• FBI uses 13 marker panel of STR’s to establish an individuals fingerprint
• Because of the number of independently inherited polymorphisms the probability of even the most common combination is tens of billions
• DNA testing can identify every person alive• FBI index contains over 5 million profiles and
has used over 45,000 to aid in almost 47,000 investigations
Our Experiment
• We will look at a VNTR on chromosome 1 called D1S80
• Has a repeat unit of 16 base pairs
• Most individuals have between 14 and 40 copies of this repeat on each copy of chromosome 1
PCR
• Polymerase chain reaction PCR is used to determine the number of repeated DNA sequences within a variable region of chromosome 1
• Each sequence will be compared to the group after being loaded into the wells of a DNA chip.
Electrophoresis
• Separates DNA fragments according to size
• Gel electrophoresis will be used to analyze the PCR products
Lab Expectations
• Take a saline solution into your mouth, swish and expel into a paper cup
• Use a micropipet to transfer 1ml of liquid into another tube
• Centrifuge for 1 minute• Pour off excess • Withdraw sample and add to a tube containing
Chelex and shake well• Boil sample for 10 minutes then cool• Centrifuge for 1 minute• Micropipet excess into a clean 1.5 ml tuve
DNA Amplification
• Micropipet buffer mix into a PCR tube
• Micropipet DNA from part 1 and centrifuge
• Label your tubes
• Store on ice
Chip Electrophoresis• Micropipet PCR sample into DNA chip well
• Place the tip of the pipet directly against the bottom of the well to avoid bubbles
• Place DNA chip into the Bioanalyzer