DNA and Introduction to Evidence

I. Every living thing is composed of cells and every cell has certain components


II. DNA - Deoxyribonucleic Acid

III. Surprise - many of our genes are similar to other creatures

Mouse and human genetic similarities

50% of our genes are found in yeast.

IV. The Human Genome Project - http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/

V. Using DNA as Evidence - Any type of organism can be identified by examination of DNA sequences. To identify individuals, forensic scientists scan 13 DNA regions that vary from person to person and use the data to create a DNA profile of that individual (sometimes called a DNA fingerprint).

Some Examples of DNA Uses for Forensic Identification
  • Identify potential suspects whose DNA may match evidence left at crime scenes
  • Exonerate persons wrongly accused of crimes
  • Identify crime and catastrophe victims
  • Establish paternity and other family relationships
  • Identify endangered and protected species as an aid to wildlife officials (could be used for prosecuting poachers)
  • Detect bacteria and other organisms that may pollute air, water, soil, and food
  • Match organ donors with recipients in transplant programs
  • Determine pedigree for seed or livestock breeds
  • Authenticate consumables such as caviar and wine

VI. How Accurate is a DNA Fingerprint?

V. Method to Create a DNA Fingerprint

Type of DNA Method  Explanation  Advantages Disadvantages and Precautions
Restriction Fragment Length Polymorphism
Stretches of DNA are cut into a variety of lengths and compared provides a clear fingerprint of DNA degraded samples don't work well, newer methods are more efficient and faster
Polymerase Chain Reaction
making multiple exact copies of DNA use of very small bits of evidence contamination & degradation
STR Analysis
Short tandem repeat
 (STR) technology is used to evaluate specific regions (loci) within nuclear DNA FBI uses 13 loci (locations) for CODIS - odds of same finger print 1:1 billion  
Mitochondrial DNA Analysis
Mitochondrial DNA analysis (mtDNA)
can be used to examine the DNA from samples that cannot be analyzed by RFLP or STR.   mothers contribute all mitochondrial DNA - does not distinguish maternal relatives
Y-Chromosome Analysis analyzes information from the Y chromosome found only in men   does not distinguish any female profiles

VII. DNA Forensics Databases

VIII. Some Interesting Uses of DNA Forensic Identification

  • Kennewick Man
    Kennewick Man was discovered in the Pacific Northwest. His ancient remains have caused problems because of competing claims for the remains by Native American groups, public officials, and scientists. Bones found in the United States that predate the arrival of Europeans are by law considered Native American, but the bones of Kennewick Man show characteristics different from Native Americans of that time period. DNA testing will be used to determine if Kennewick Man's DNA is similar to that of other Native Americans.


  • Disappeared Children in Argentina
    Numerous people (known as "the Disappeared") were kidnapped and murdered in Argentina in the 1970s. Many were pregnant. Their children were taken at birth and, along with other young kidnapped children, were raised by their kidnappers. The grandparents of these children are now looking for them. Read an article about a DNA researcher who has been helping them.


  • Tomb of the Unknowns


  • The Murdered Nicholas Romanov, the Last Czar of Russia, and His Family


  • Son of Louis XVI and Marie Antionette
    PARIS, Apr 19, 2000 (Reuters) -- Scientists cracked one of the great mysteries of European history by using DNA tests to prove that the son of executed French King Louis XVI and Marie-Antoinette died in prison as a child. Royalists have argued for 205 years over whether Louis-Charles de France perished in 1795 in a grim Paris prison or managed to escape the clutches of the French Revolution. In December 1999, the presumed heart of the child king was removed from its resting place to enable scientists to compare its DNA make-up with samples from living and dead members of the royal family -- including a lock of his mother Marie-Antoinette's hair.


  • Peruvian Ice Maiden
    The Ice Maiden was a 12-to-14-year old girl sacrificed by Inca priests 500 years ago to satisfy the mountain gods of the Inca people. She was discovered in 1995 by climbers on Mt. Ampato in the Peruvian Andes. She is perhaps the best preserved mummy found in the Andes because she was in a frozen state. Analysis of the Ice Maiden's DNA offers a wonderful opportunity for understanding her genetic origin. If we could extract mitochondrial DNA from the Ice Maiden's tissue and successfully amplify and sequence it, then we could begin to trace her maternal line of descent and possibly locate past and present relatives.


  • African Lemba tribesmen
    In southern Africa, a people known as the Lemba heed the call of the shofar. They have believed for generations that they are Jews, direct descendants of the biblical patriarchs Abraham, Isaac, and Jacob. However unlikely the Lemba's claims may seem, modern science is finding a way to test them. The ever-growing understanding of human genetics is revealing connections between peoples that have never been seen before.


  • Super Bowl XXXIV footballs and 2000 Summer Olympic souvenirs
    The NFL used DNA technology to tag all of the Super Bowl XXXIV balls, ensuring their authenticity for years to come and helping to combat the growing epidemic of sports memorabilia fraud. The footballs were marked with an invisible, yet permanent, strand of synthetic DNA. The DNA strand is unique and is verifiable any time in the future using a specially calibrated laser.

    A section of human genetic code taken from several unnamed Australian athletes was added to ink used to mark all official goods everything from caps to socks from the 2000 Summer Olympic Games. The technology is used as a way to mark artwork or one-of-a-kind sports souvenirs.


  • Migration patterns
    Evolutionarily stable mitochondrial DNA and Y chromosomes have allowed bioanthropologists to begin to trace human migration patterns around the world and identify family lineages. An example:


  • Wine heritage
    Using DNA fingerprinting techniques akin to those used to solve crimes and settle paternity suits, scientists at the University of California, Davis, have discovered that 18 of the world's most renowned grapevine varieties, or cultivars, including varieties long grown in northeastern France such as Chardonnay, the "king of whites," and reds such as Pinot and Gamay noir, are close relatives.


  • DNA Banks for Endangered Animal Species


  • Poached Animals


  • Declining Grizzly Bear Population


  • Snowball the Cat
    A woman was murdered in Prince Edward Island, Canada. Her estranged husband was implicated because a snowy white cat hair was found in a jacket near the scene of the crime, and DNA fragments from the hair matched DNA fragments from Snowball, the cat belonging to the husband's parents. M. Menotti-Raymond et al., "Pet cat hair implicates murder suspect," Nature, 386: 774, 1997.


  • Angiosperm Witness for the Prosecution
    The first case in which a murderer was convicted on DNA evidence obtained from a plant was described in the PBS TV series, "Scientific American Frontiers." A young woman was murdered in Phoenix, Arizona, and a pager found at the scene of the crime led the police to a prime suspect. He admitted picking up the victim, but claimed she had robbed him of his wallet and pager. The forensic squad examined the suspect's pickup truck and collected pods later identified as the fruits of the palo verde tree (Cercidium spp.). One detective went back to the murder scene and found several Palo Verde trees, one of which showed damage that could have been caused by a vehicle. The detective's superior officer innocently suggested the possibility of linking the fruits and the tree by using DNA comparison, not realizing that this had never been done before. Several researchers were contacted before a geneticist at the University of Arizona in Tucson agreed to take on the case. Of course, it was crucial to establish evidence that would stand up in court on whether individual plants (especially Palo Verde trees) have unique patterns of DNA. A preliminary study on samples from different trees at the murder scene and elsewhere quickly established that each Palo Verde tree is unique in its DNA pattern. It was then a simple matter to link the pods from the suspect's truck to the damaged tree at the murder scene and obtain a conviction. [WNED-TV (PBS - Buffalo, N.Y.)]