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Category Archives: DNA

Blue-eyed Mesolithic Caveman?

Was there an ancient Marlboro Man? Cool, swarthy. handsome?

DNA obtained from the wisdom tooth of the 7000-year-old remains of an European Mesolithic (Middle Stone Age) hunter-gather has been analyzed and suggests that the man had dark skin and hair, blue eyes, and was likely lactose intolerant.

Artist Impression of Mesolithic Hunter-gatherer

Artist Impression of Mesolithic Hunter-gatherer

We are all familiar with DNA’s use in solving crimes by matching a suspect to a crime scene and, particularly mitochondrial DNA (mtDNA), in ancestry investigations. DNA analysis can also often reveal sex, race, and hair and eye color.

Mesolithic Skull

Mesolithic Skull

Mesolithic Life in Europe Before the Curse of Farming: http://archaeology.about.com/od/mesolithicarchaic/qt/Mesolithic.htm

Historic Timeline: http://www.historiclandscape.co.uk/exploring_time.html

Stone Age Timelines: http://www.historiclandscape.co.uk/exploring_time.html

 
 

Jack The Ripper Identified?

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A new book titled Naming Jack The Ripper by Russell Edwards presents information that the author feels solves the famous Jack The Ripper case. The five murder-mutilations that occurred in London’s East End during 1888 have baffled criminologists for over a century. Several suspects have been identified but none have been proven to be the real Ripper. So who is Jack? According to Edwards, it’s Aaron Kosminski, a Polish immigrant who had “mental issues,” was 23 years old at the time of the killings, and who ultimately died in an insane asylum many years later at the age of 53. He never confessed or anything convenient like that, but he has long been one to the prime suspects.

So is he really Jack? Maybe. Here are some articles. Make up your own mind.

Daily Mail UK: http://www.dailymail.co.uk/news/article-2746321/Jack-Ripper-unmasked-How-amateur-sleuth-used-DNA-breakthrough-identify-Britains-notorious-criminal-126-years-string-terrible-murders.html

Independent UK: http://www.independent.co.uk/news/science/has-jack-the-rippers-identity-really-been-revealed-using-dna-evidence-9717036.html

Mirror UK: http://www.mirror.co.uk/news/uk-news/jack-ripper-murder-mystery-solved-4177665

 

Jack-the-Ripper-shawl-4

 

Crime and Science Radio: Taking A Bite Out Of Crime: An Interview with Forensic Dentist Dr. Michael Tabor

Join Jan Burke and DP Lyle as they explore the world of forensic dentistry with Dr. Mike Tabor, Chief Forensic Dentist of the State of Tennessee Office for the Medical Examiner. Learn exactly how forensic dentistry aids in corpse identification and dig into some of Dr. Tabor’s most famous cases.

 

MTabor

 

BIO: In the spring of 1973, Mike Tabor embarked on a journey that would take him down a path he could have never imagined. With a freshly earned DDS, Dr. Mike Tabor left Carson-Newman College and The University of Tennessee College of Dentistry, and began his career as a family dentist. In 1983, Dr. Tabor’s work as a family dentist took a unique turn and he found himself immersed in the highly specialized field of forensic dentistry. As one of only a handful of forensic dentists in the United States, Dr. Tabor became a highly sought after expert in this field, performing identifications and examinations on homicide victims, as well as aiding police departments, investigators and medical examiners all over the Country in the prosecution of thousands of crimes.

In September of 2001, Dr. Tabor found himself in New York, at the site of the World Trade Center terror attacks, aiding in the identification of countless victims. For Mike Tabor, this infamous and historical event forever changed his life. As a forensic dentist, Mike was no stranger to the examination of deceased victims, but the horrors of September 11th would not allow Mike, the man, to separate himself from his work as Dr. Tabor, the forensic dentist. September 11, 2011 left a lasting and emotional impression on Mike and gave him a completely new perspective on life and loss.

Dr. Mike Tabor was a featured contributor and has written an entire chapter for the Internationally Accredited Textbook, Forensic Dentistry. He has served as the president of the Tennessee State Board of Dental Examiners, and is currently the Chief Forensic Dentist for The State of Tennessee Office of the Medical Examiner, and is an energetic, engaging and highly respected and sought after public speaker. He makes his home in Nashville, with his beautiful wife, Karen and their two snow white canine children, Mollie and Millie. He is the proud father of two grown children and the doting grandfather of seven adorable grandchildren.

LISTEN: 

LINKS:

Dr. Michael Tabor’s Website: http://www.drmiketabor.com

Dr. Michael Tabor’s Blog: http://www.drmiketabor.com/blog/

Walk Of Death: http://www.amazon.com/Walk-Of-Death-Forensic-Novel/dp/1490533737

American Society of Forensic Odontology: http://asfo.org

How Stuff Works: Forensic Dentistry: http://science.howstuffworks.com/forensic-dentistry.htm

Forensic Odontology: http://www.nlada.org/forensics/for_lib/Documents/1124743291.01/425lect16.htm

International Association for Identification: http://www.theiai.org/disciplines/odontology/

Forensic Dentistry Online: https://www.forensicdentistryonline.org

Medscape: Forensic Dentistry: http://emedicine.medscape.com/article/1771750-overview

Wikipedia: Forensic Dentistry: http://en.wikipedia.org/wiki/Forensic_dentistry

Forensic Dentistry Careers: http://criminologycareers.about.com/od/Forensic-Science-Careers/a/Career-Profile-Forensic-Odontologist.htm

Animal and Human Bite Mark Analysis: http://www.forensic.to/webhome/bitemarks/

Crime Library: Bite Marks As Evidence: http://www.crimelibrary.com/criminal_mind/forensics/bitemarks/1.html

Writers Forensics Blog: Guest Blogger: Dr. Mike Tabor: Anatomy Of A Forensic Dental Identification: http://writersforensicsblog.wordpress.com/2014/06/05/guest-blogger-mike-tabor-anatomy-of-a-forensic-dental-identification/

 

WalkofDeath

 

Guest Blogger: Daphne Holmes: How DNA Testing Helps Determine Paternity

DNA

 

How DNA Testing Helps Determine Paternity

The impetus for determining the paternity of a child likely dates back to the most primitive tribal cultures. Particularly in patriarchal cultures where females were regarded as the property of males, it was deemed important to ensure that a man’s “property” had not been shared, and that the virtue of the female was beyond question. As societies became more sophisticated, the need to establish paternity became as much an economic issue as a moral one. In modern cultures, paternity testing is used primarily to establish whether or not a man is responsible for providing financial support to a child, as well as determining whether the child carries any of the father’s genetic predispositions for health challenges.

Physical appearance – In more primitive cultures (some of which continue to flourish), the objectives behind determining the paternity of a child were culturally and/or emotionally based. If a child was born who lacked identifying characteristics of either parent, it was frequently assumed that the father was someone other than the woman’s mate. The repercussions to the mother were quite severe, often culminating in her death. Unfortunately – especially for the women – the comparison of obvious physical traits was highly subjective, and many women suffered dire consequences, even if their husband/mate was indeed the biological father.

Blood typing – With the early 20th century discovery that different individuals had different blood types, and the recognition in the 1920s that those blood types were genetically inherited, a more accurate means of determining paternity came into common use. It was discovered that by comparing the parents’ blood types, it was possible to determine the most likely blood type of the child. While this was admittedly a step above the “he has his father’s eyes” paternity test, it was still only about 30% accurate.

Serological testing – It was discovered in the 1930s that specific proteins not considered during blood typing could establish the presence of genetically inherited antigens that would more accurately identify the child’s biological father. Unfortunately, serological testing only improved the accuracy of paternity testing to about 40%. Hardly conclusive evidence.

Tissue typing – In the 1970s, the human leukocyte antigen (HLA) was discovered in abundance within white blood cells. When samples of this genetically inherited antigen taken from the mother and child were compared to the sample taken from the father, paternity could be established with roughly 80% accuracy. While this was a significant improvement over previous methods, the collection procedure itself was unpleasant, and the size of the sample required made it hazardous to the child, particularly if the child was less than six months old. Obviously, more work needed to be done.

DNA testing (RFLP) – In the 1980s, the technique called restriction fragment length polymorphism (RFLP) was discovered that looked at a significantly wider spectrum of variables in the blood than had been analyzed with earlier techniques. It was discovered that the offspring of two parents would have half the unique characteristics of each parent. This technique elevated the accuracy of paternity testing to the level of statistical certainty. Unfortunately, the amount of blood required for accurate sampling was, like tissue sampling, large, posing potential problems for the child. In addition, the potential for genetic mutations in the child could render a false negative, indicating that neither the woman or the man was the child’s biological parents. For these reasons, RFLP testing has been all but abandoned.

DNA Testing (PCR) – By the 1990s, the RFLP testing was replaced by the polymerase chain reaction (PCR) technique. This technique involves the computerized replication of DNA collected from even a minuscule sample that is collected anywhere on the individual’s body, then comparing the subjects’ profiles. In addition to requiring a very small sample (typically via an oral swab), the subject is not submitted to discomfort as in earlier test techniques, and the computerized analysis takes far less time, while still providing accuracy at the level of statistical certainty, 99.99%.

Author: Daphne Holmes contributed this guest post. She is a writer from www.ArrestRecords.com and you can reach her at daphneholmes9@gmail.com.

 

 

Guest Blogger: EE Giorgi: I Am My Mother’s Chimera. Chances Are, So Are You

For years now the concept of a “genetic chimera” has sparked the imagination of writers: from Stephen King to Michael Crichton, from CSI to The Office. The idea that an individual could harbor his/her own twin is creepy and intriguing at the same time, not to mention it offers the perfect escape from DNA testing in a police procedural plot.

But if you think that “chimeras have been done already,” think again. All fictional works written so far have exploited the concept of tetragametic chimeras, which results from combining two or more genetically distinct organisms. In humans, this happens when two fertilized eggs fuse together during the first hours of life in the womb.

Yet Mother Nature has invented many other forms of chimerism.

Some genetic defects/mutations can lead to individuals with genetically distinct cells in their body. Usually these defects involve anomalies in the number of chromosomes, but there are also asymptomatic cases, like for example animals whose coat is a patchwork of different colors, as in tortoiseshell cats. This type of chimerism is called mosaicism. Contrary to tetragametic chimeras, which originate from two or more individuals fused together, mosaics originate from a single individual. People whose eyes have different colors are also an example of genetic mosaicism.

Tortoiseshell cat (Source: Wikipedia)

Tortoiseshell cat (Source: Wikipedia)

 

Scientists claim that chimeras are much more common than we think. Chances are, you could be your own twin. But how surprised would you be if I told you that you are actually far more likely to be your mother’s chimera than your unborn sibling’s?

“Microchimerism refers to a small number of cells (or DNA) harbored by one individual that originated in a genetically different individual” (Gammill and Nelson, 2010).

An individual receiving a donor transplant or a blood transfusion is an example of microchimerism. Yet the most common form of microchimerism happens during pregnancy. There’s an ongoing two-way cell trafficking across the placenta, and these exchange cells can actually proliferate long term in the host’s body: fetal cells can be found in the mother years after she gave birth. In fact, because even spontaneous abortions cause fetal cells to be released into the mother’s body, women who became pregnant but never gave birth can also harbor this form of microchimerism.

Mystery writers are familiar with the “Jane Doe scenario”: an unidentified woman that lands on the medical examiner’s table. One of the many things the ME can learn about this woman with today’s technology is whether or not she was ever pregnant—even if the pregnancy ended with a spontaneous abortion. With a single test the ME can find male DNA in Jane Doe and deduce that at some point she was pregnant with a baby boy. A baby girl can also be detected, but it requires more than one test.

Just like fetal cells can be found in the mother years after she has given birth, the inverse is also true: maternal cells have been found in fetal liver, lung, heart, thymus, spleen, adrenal, kidney, pancreas, brain, and gonads. What’s surprising is that in either case (mother-to-fetus transfer, or, vice versa, fetus-to-mother transfer), the extraneous cells migrate to a certain tissue and, once there, they are able to differentiate and proliferate, acting at all effects as if they were engrafted. One paper found circulating maternal cells in 39% of the study subjects (Loubiere et al. 2006).

But even if you are not your own twin, even if you don’t harbor cells from your mother or your child, even then chimeras are closer than you think. Because we all originated from a chimera: roughly 10% of our DNA is made from viral genes, and how this came to happen is a fascinating story.

A long time ago a virus infected a sperm cell or oocyte of one of our ancestors. Once there, the genetic material from the virus fused with the genetic material of the cell —- that’s an old trick viruses play so they can replicate. Except this particular virus never replicated. The sperm or oocyte was fertilized and became a fetus, and that fetus now carried the bit of viral DNA. The viral genes were “stuck”, no longer able to replicate, and thus effectively silenced.

Finally, the last form of chimerism I would like to discuss is far less known because it belongs to a fairly new field: epigenetics.

Genes are packaged inside the nucleus, some deeply hidden inside, and some exposed so that they can be easily “translated” into proteins. This configuration can change in time, as genes can move from the inside of the nucleus and become exposed, while others previously exposed can become hidden. Life events, changes in the environment or in diet, stress, and traumas can potentially affect these mechanisms, causing some genes to turn on while turning off others.

Epigenetics is the study of all mechanisms that can affect gene silencing (turning the genes “off”) and gene expression (turning the genes “on”). In other words, it addresses the question: what causes some genes to shift from being hidden (silenced) to becoming suddenly exposed (expressed) and other genes instead to suddenly become hidden (silenced)?

The amazing thing is that these epigenetic mechanisms are not encoded in the DNA, yet there have been studies that have shown that epigenetic changes caused by stress or diet can indeed be carried over for the next two-three generations.

You’ve probably guessed it by now: an individual whose cells express distinct genes within the same tissue is called an epigenetic chimera.

From a writer’s point of view, this kind of chimerism lends itself to many more scenarios than the genetic one. For one thing, it is much more complicated to detect as the defects no longer lie in the genes themselves, but rather in which genes are expressed and which aren’t. At the same time, epigenetic disorders can give rise to any sort of dysfunctional phenotypes. And you have a wide range of “life events” that could potentially trigger the “sudden change” in your character(s): viruses can certainly mess up with the cells’ signaling and turn on forgotten genes; an accident or physical trauma can spike new sensations/symptoms (have you ever heard of someone’s sense of smell suddenly spiking after a car accident?); a change in diet/environment; etc.

Vampires and zombies may have been done already. But there’s still a lot of room for chimeras of all kinds.

 

EEGiorgi

EEGiorgi

 

E.E. Giorgi is a scientist, a writer and a photographer. She loves to blog about science for the curious mind, especially the kind that sparks fantastic premises and engaging stories. She has done scientific consultations for writers such as Autumn Kalquist (Legacy Code) and bestselling author Carol Cassella (Oxygen). E.E.’s detective thriller CHIMERAS, a hard-boiled police procedural with a genetic twist, is now available on Amazon.

Link to Blog: http://chimerasthebooks.blogspot.com/

Link to book on Amazon: http://www.amazon.com/dp/B00JI6UNPE

Chimeras Cover

Previous Posts on Chimerism:

 

Q&A: How Could My Sleuth Recognize a Chimera?: http://writersforensicsblog.wordpress.com/2010/07/05/qa-how-could-my-sleuth-recognize-a-chimera/

Organ Creation and Harvesting: Reality Imitating Art: http://writersforensicsblog.wordpress.com/2013/07/18/organ-creation-and-harvesting-reality-imitating-art/

Guest Blogger: Elena Giorgi: Deep DNA Sequencing: http://writersforensicsblog.wordpress.com/2011/09/22/guest-blogger-elena-giorgi-deep-dna-sequencing/

Human Chimerism: Mindboggling DNA Tests Gone Wrong-Guest Blogger: http://writersforensicsblog.wordpress.com/2010/06/24/human-chimerism-mindboggling-dna-tests-gone-wrong-guest-blogger/

 
2 Comments

Posted by on April 9, 2014 in DNA, Guest Blogger, Medical Issues

 

Cat DNA Solves Another Homicide

TINKER

TINKER

 

Tinker doesn’t look like a snitch. But then again, neither did Snowball. Snowball is a very famous cat. It was Snowball’s DNA that led to the solution of a 1994 murder and it represented the first time cat DNA had been used to solve a crime.

From HOWDUNNIT: FORENSICS:

FORENSIC CASE FILES: SNOWBALL THE CAT

In 1994, Shirley Duguay of Prince Edward Island disappeared. A few days later her corpse was discovered in a shallow grave along with a leather jacket, which was soaked with her blood and dotted with white cat hairs. Her estranged husband, Douglas Beamish, owned a white cat named Snowball. DNA in blood taken from Snowball matched that of the cat hairs found at the burial site, proving that those hairs came from Snowball and no other white cat. Beamish was convicted, marking this case the first time that animal DNA was used to gain a conviction.

Tinker has now followed suit in a very interesting case from Britain.

 

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Do Identical Twins Have Different DNA?

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DNA profiling is considered the gold standard for individual identification. DNA-containing bodily fluids found at crime scenes can often be linked to the perpetrator with a high degree of accuracy, often measured in one per billions. It is highly individual and therefore highly accurate for identifying a given individual.

But since identical twins begin as the same fertilized egg, they have identical genetic material (DNA). After fertilization, the fertilized egg divides into two cells. To produce identical twins, these two cells separate and then each progresses forward to produce an individual. This results in two identical individuals with identical DNA. Or does it?

Twins egg:sperm

 

Standard DNA testing uses the concept of Short Tandem Repeats (STR’s). STR’s are simply short segments of DNA that repeat in certain areas of the very long DNA strand found in all of us. The number of these repeats in the various locations are what allow DNA profiling to distinguish individuals so accurately. This is a complex, though not really difficult to understand, technique which is discussed in great detail in two of my books: Forensics For Dummies and Howdunnit: Forensics.

DNA Profile

But scientists have known for years that the DNA of identical twins is not perfectly identical. It might or might not start out that way at that first cell division but for sure as the cells divide and the individual grows within the uterus, minor DNA changes can occur. These are on the level of the base pair sequences that make up the DNA chain.

Another DNA technique called Single Nucleotide Polymorphism (SNP) actually looks at each base in the DNA strand and uses this for comparison with another strand to determine if they came from the same individual. This is the direction that DNA testing is going but for now STR remains the method of choice.

Identical twins would look the same using STR analysis but a deeper analysis using SNP would reveal variations, thus allowing identification and separation of two identical twins. Let’s say, blood is left at a crime scene and that blood is matched to a particular individual. Let’s further say that this individual is an identical twin. STR DNA analysis would not distinguish between these two brothers, But if SNP is employed, the one who left the blood at the scene can be distinguished from his identical twin.

The recent French serial rape investigation involving identical twins Yohan and Elwin would be a case in point. Applying the SNP technique in this situation would likely solve the case.

Pretty cool stuff.

Howdunnit Forensics Cover

 

From HOWDUNNIT: FORENSICS:

SINGLE NUCLEOTIDE POLYMORPHISM

Single nucleotide polymorphism (SNP) is a new technique that will likely see increased use in the future. The major problem at present is that it is expensive. We saw that RFLP fragments were fairly long, a drawback that lessens their value in degraded or damaged samples (discussed later). This problem was circumvented by the discovery of STRs, which are very short fragments. But, what if the DNA examiner could use single nucleotide bases as the standard for matching? This would increase the discriminatory power of DNA even further. This is what SNP does.

Let’s say that two sequenced DNA strands looked like this:

CGATTACAGGATTA and CGATTACAAGATTA

If we searched for an “ATTA” STR repeat, these two strands would be indistinguishable

since both have two ATTA repeats. But, with single nucleotide analysis the strands differ by a single base: The ninth base in the first sequence is guanine (G), while it is adenine (A) in the second one. SNP can be used with restriction enzymes in the RFLP technique, or with PCR, where it can be easily automated. Theoretically, this will allow for discriminating two DNA samples based on a single nucleotide difference.

 
 
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