Genetic Identity and Forensics

Noninvasive Prenatal Genetic Testing Using Circulating Cell-Free DNA

Posted on by Terri Sundquist

Expectant MotherScientists have known for some time that fetal DNA can be detected in the maternal bloodstream during pregnancy (1). Up to 10% of circulating cell-free-DNA (ccfDNA) can be attributed to the fetus. Fetal ccfDNA is released from the placenta, mainly through apoptosis, and enters the maternal bloodstream, where it can be easily collected and detected by PCR amplification. This method of collection has a much lower risk of miscarriage compared to more invasive collection methods such as amniocentesis and chorionic villus sampling.

Amplification of fetal ccfDNA enables a number of prenatal genetic testing such as gender determination and detection of fetal aneuploidy and other mutations. Testing of ccfDNA also allows identification of fetuses with a higher risks of hemolytic disease of the newborn (erythroblastosis fetalis) due to expression of the Rh factor in an Rh– negative mother, who can develop antibodies against the Rh factor and mount an immune response against fetal red blood cells. Finally, ccfDNA allows prenatal paternity determination (2). However, these tests have limitations.

Continue reading “Noninvasive Prenatal Genetic Testing Using Circulating Cell-Free DNA”

Molecular Autopsies in the Whole Genome Sequencing Era

Posted on by Terri Sundquist

Engraving of the human heart by T. Milton, 1814. Image courtesy of Wikimedia Commons.
Engraving of the human heart by T. Milton, 1814. Image courtesy of Wikimedia Commons.
Every year, nearly 8 million people die from sudden cardiac death, which is defined as the unexpected death of a seemingly healthy person due to malfunctions in the heart’s electrical system and loss of cardiac function. Although sudden cardiac death (SCD) is usually associated with mature adults, SCD claims thousands of young lives every year. In most cases, the cause of death can be determined by autopsy or toxicological analysis, but up to 30% of these premature deaths have no apparent cause, leaving medical examiners and family members of the young victims to wonder what happened.

In cases where traditional pathological examinations cannot provide insight into causation, medical examiners are increasingly turning to molecular autopsies to determine if there is an underlying genetic factor that contributed to a person’s death.

Continue reading “Molecular Autopsies in the Whole Genome Sequencing Era”

Forensic Science in Search of the ‘Disappeared’

Posted on by Terri Sundquist

By Fredy Peccerelli

Guatemala’s method of uncovering human rights violations can help other post-conflict areas, says Fredy Peccerelli.

Skeleton Teeth

During Guatemala’s internal armed conflict (1960–1996) almost 200,000 people are thought to have been killed or ‘disappeared’ at the hands of repressive and violent regimes. Those lives matter. Their families’ demands are clear: they want to know what happened to their loved ones and they want their remains returned. They need truth and justice.

Using forensic sciences, the Forensic Anthropology Foundation of Guatemala (FAFG) is assisting families by returning their loved ones’ remains, promoting justice, and setting the historical record straight.

Continue reading “Forensic Science in Search of the ‘Disappeared’”

From Death Row to Exoneration Thanks to DNA Testing

Posted on by Terri Sundquist
Hands of man prisoner gripping rusty prison bars

Imagine being convicted of a crime for which you are not guilty—not some minor crime, but one of the most heinous crimes imaginable: the rape and murder of a young girl. Would you feel shock and anger at the injustice? Disappointment in the legal system that could make such a horrible error? Sadness and depression at the thought of spending time imprisoned for a crime that someone else committed? Probably all of those emotions and more. At your sentencing hearing, the situation gets worse; you are sentenced to death. Now, this horrible crime will prematurely claim the life of two innocents: the young girl and you.

This is the situation that Kirk Bloodsworth faced in 1985: a death sentence for the rape and murder of 9-year-old Dawn Hamilton. Although Bloodsworth didn’t know it at the time, DNA testing would eventually prove his innocence and save his life.

Continue reading “From Death Row to Exoneration Thanks to DNA Testing”

Mitochondrial DNA Typing in Forensics

Posted on by Anupama Gopalakrishnan

23540687_lMitochondria, often thought of as powerhouses of the cell, are fascinating eukaryotic organelles with a double-layered membrane and their own genome. Mitochondrial DNA (Mt DNA) is typically about 16570 bases, circular, highly compact, haploid and contains 37 genes, all of which are essential for normal mitochondrial function. Thirteen of these genes provide instructions for making enzymes involved in oxidative phosphorylation, a process that uses oxygen and simple sugars to create adenosine triphosphate (ATP), the cell’s main energy currency. The remaining genes code for transfer RNA (tRNA) and ribosomal RNA (rRNA) which are necessary for translating messenger RNA transcribed from nuclear DNA, into protein molecules.

One of the most important characteristics of mitochondrial genome that is relevant to field of forensics is the copy number. Continue reading “Mitochondrial DNA Typing in Forensics”

DNA Reveals the Identity of Jack the Ripper?

Posted on by Terri Sundquist

A wanted poster for Jack the Ripper, who was also known as Leather Apron. Image courtesy of the British Museum
A wanted poster for Jack the Ripper, who was also known as Leather Apron.
Image courtesy of the British Museum

In the late 1800s, Victorian England was mesmerized and horrified by a series of brutal killings in the crowded and impoverished Whitechapel district. The serial killer, who became known as “Jack the Ripper”, had murdered and mutilated at least five women, many of whom worked as prostitutes in the slums around London. None of these murders were ever solved, and Jack the Ripper was never identified, although investigators interviewed more than 2,000 people and named more than 100 suspects. Now, 126 years after the murders, a British author, who coincidentally has just published a book on the subject, is claiming that DNA analysis has revealed the identity of the notorious killer. DNA is often thought to be the “gold standard” of human identification techniques, so why is there so much skepticism surrounding this identification?
Continue reading “DNA Reveals the Identity of Jack the Ripper?”

PowerQuant System: Tool for informed casework sample processing decisions

Posted on by Anupama Gopalakrishnan

CottonSwabsIdentification of a crime perpetrator on the basis of DNA fingerprinting is not as easy as some of the CSI shows on television make it out to be. A sample such as blood stain, touch sample or body fluid retrieved at a crime scene is often a challenge for DNA analysts. In many instances, the samples are limited in quantity, found in dirty conditions, exposed to harsh environmental factors and are mixtures of more than one DNA—human and/or non-human. One of the most important aspects of the workflow to successfully obtain a DNA fingerprint profile is accurate quantification of human amplifiable DNA. The more information gleaned from the sample, the better equipped the DNA analyst is to determine the best course of action for obtaining a usable short tandem repeat (STR) profile from challenging samples. Therefore, Promega has developed the PowerQuant™ System, a probe-based 4-target, 5-dye real-time PCR method to a) determine human and male DNA concentrations in a sample, b) detect possible PCR inhibitors c) identify possible mixtures and d) measure DNA integrity. Continue reading “PowerQuant System: Tool for informed casework sample processing decisions”

How a Magazine Ad Helped Convict a Rapist

Posted on by Terri Sundquist
Trial

In May of 1986, a woman in Orange County, Florida, was surprised by a man who entered her apartment and raped her at knifepoint. Despite the fact that she got a glimpse of his face, the chances of identifying and convicting her rapist were slim. Although law enforcement officers did their best to identify the perpetrator, their investigative techniques in the case were limited compared to our current set of forensic tools. That changed when Jeffrey Ashton, an assistant attorney for the state of Florida, saw an advertisement for DNA-based paternity testing in a magazine and began to wonder if DNA testing could also be used to identify the man responsible for the attack.

Continue reading “How a Magazine Ad Helped Convict a Rapist”

DNA Gives Hope to Human Trafficking Victims

Posted on by Terri Sundquist
Neglected child

The statistics are grim. In 2013, human rights agencies estimate that as many as 29.8 million people worldwide are victims of human trafficking (1), forced into debt bondage or marriage or sold as soldiers or sex workers. Many of these victims are children. Very few of them are ever identified (less than 0.2% of victims in 2013).

Most of us like to think that this sort of thing doesn’t happen in our modern world, but the recent abduction of 276 school girls in Nigeria is just more proof that it does. Human trafficking is big business, and a single Nigerian woman can command as much as $78,000 on the black market. Meanwhile, others are being bought and sold for less money than some of us spend on food in a day. Fortunately, human rights and law enforcement agencies are developing tools to combat this problem. In addition to conventional investigation methods such as surveillance, sting operations and interviews with victims and alleged perpetrators, these agencies are recruiting scientists to join this fight by implementing cutting-edge DNA-based human identification methods.

Continue reading “DNA Gives Hope to Human Trafficking Victims”

Ancient Origins of a Human Gene Associated with Diabetes

Posted on by Terri Sundquist

Ancient peopleRecently, researchers of the SIGMA Type 2 Diabetes Consortium published a paper in Nature identifying a new locus associated with a higher risk of type 2 diabetes (1). Considering the increasing prevalence of this metabolic disease in today’s sugar-filled world, any discovery that helps us understand diabetes is exciting news. However, the most interesting discovery published in this paper might not be this new gene variant but rather the origin of this variant in modern human populations: Neandertals.

Continue reading “Ancient Origins of a Human Gene Associated with Diabetes”