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