DNA Facts Watson & Crick 1953 Contains all Genetic info ½ from each parent ¾ like siblings Double helix Unique????? In all cells with nuclei Made of nucleotides with nitrogen

bases ATCG 98.5% is Junk… non-coding DNA,

that’s what makes you unique Also found in mitochondria…from mom

Sources of DNA

Blood Saliva Semen Vaginal fluid Skin cells Hair with follicle

Obtaining DNA from a suspect A warrant is needed Garbage can be used……. Tissue, coffee cup, straw Certain convicted felons in NYS must submit DNA sample Since January 1, 1996, the law in New York State has required

offenders convicted of certain felonies to submit biological samples (formerly blood and more recently buccal samples swabbed from the inside of the cheek) for DNA profiling through laboratory analysis.

The resulting records of offender DNA profiles are organized into a centralized index within the State DNA Data Bank—a part of CODIS, the national Combined DNA Index System developed by the FBI.

CODIS… Combined DNA INDEX System DNA database funded by the United States

Federal Bureau of Investigation (FBI). It is a computer system that stores DNA profiles

created by federal, state, and local crime laboratories in the United States, with the ability to search the database to assist in the identification of suspects in crimes.

Congress formally authorized the FBI to operate CODIS and set national standards for forensic DNA testing. Although the Act was passed in 1994, CODIS did not become fully operational until 1998.

Creating a DNA Profile

Extraction Use of Restriction Enzymes Amplification Electrophoresis

Extraction

DNA is extracted from the cells

Strong detergents are used to remove the DNA from the membranes that hold it.

You can do DNA extraction at home… All the materials and equipments to carry out the experiment are items commonly found in the household. Pour 3/8 cup of water into a cup. Add 1/4 teaspoon of salt and clear liquid soap into the cup, and stir for the salt to dissolve. The soap causes the

cell walls to break up, freeing the DNA inside. The salt is for keeping the DNA molecules together.

Place the organic materials into the sandwich bag or blender and mash or crush until completely pulverized. This is to break the cells apart.

Add 2 teaspoons of the soap-salt solution to the bag. Mix gently by compressing or rocking the bag for at least 1 minute.

Pour the mixture through coffee filter into a clear jar. Let it drain into the jar for 10 minutes.

DNA extraction at home Meanwhile, pour 1/4 coup of rubbing

alcohol into another clear jar and put the jar in the freezer or a bowl of ice. The alcohol helps strip the water molecules from the outside of the DNA molecules, causing the molecule to collapse on itself and separate from the proteins in the solution.

After 10 minutes have elapsed, pour the strained liquid into the alcohol. Let the jar sit still for at least 5 minutes. The final product contains a layer of proteins and a cloudy layer of DNA clumped together. The naked eyes cannot resolve the individual macromolecules within.

Use of Restriction Enzymes

Used to cut the DNA into shorter fragments The enzymes cut the DNA at a specific

sequence of bases (recognition site) These fragments are called VNTRs (variable

number tandem repeats) and STRs (short tandem repeats)

Use of Restriction Enzymes

VNTRs

short sequences of DNA that contain 9-80 bases with a repeated sequence

ex. CATACAGAC CATACAGAC CATACAGAC

In one person it might repeat 3x in another 7x

STRs

More useful in DNA analysis Shorter than VNTRs 2-5 bases repeated Ex. GATA GATA GATA GATA GATA More accurately used, easier to separate Degraded DNA can also be analyzed

Amplification

PCR (polymerase chain reaction) used to amplify the amount or DNA Generates multiple identical copies of small amounts of DNA

Billions of copies of the DNA sample can be made in a few hours

Invented in 1993 by Dr. Gary Mullis Used in Jurassic Park

PCR

Electrophoresis

Separates the DNA fragments by size and polarity in an electric field

The DNA moves through the field by size, smaller fragments move more quickly through the gel

The fragments form band with the shortest fragments closest to the (+) end

Gel Electrophoresis Apparatus

Electrophoresis

The RESULTS……..

Uses of a DNA profile

Match Crime scene DNA to suspect’s DNA Eliminate suspects Paternity/maternity tests ID family members ID human remains Free those falsely accused