Author: Darcia Schweitzer

So NASA Found Some New Exoplanets…Now What?

Posted on by Darcia Schweitzer
34412848-March-8-Planets-600x600-WEB

You have probably heard a lot of excitement over NASA’s recent announcement about the discovery of seven earth-size planets found orbiting around the star TRAPPIST-1, which is part of the constellation Aquarius.

These exoplanets are notable because they exist within the habitable zone of the star (nicknamed Goldilocks planets because this area is not too hot and not too cold) and are probably rocky with the potential to contain water on their surface.

A lot of the enthusiasm revolves around the hope that one of these exoplanets might harbor extraterrestrial life or could be suitable for human inhabitants. Of course, many further observations must be made to determine if these scenarios are plausible, not to mention the huge advances in technology that would need to occur so we could actually verify the planetary conditions or send humans 40 light-years away.

Continue reading “So NASA Found Some New Exoplanets…Now What?”

Familial Searching Solves Cold Cases—At What Cost?

Posted on by Darcia Schweitzer

A cold case that had stumped investigators for nearly 41 years was solved last month. The 1976 sexual assault and murder of Karen Klass, ex-wife of Righteous Brother’s singer Bill Medley, shocked her Hermosa Beach, CA community and captured the public interest. Failing to make any arrests for decades, detectives were able to use DNA evidence to eliminate suspects in 1999 but were unable to find a database match. In 2011, investigators decided to try a new technique called a familial search and, after a few attempts, successfully identified the perpetrator.

DNA-Handcuffs-double-exposure-R2

Familial searching (FS) involves taking a DNA profile obtained from a crime scene and comparing it to profiles in CODIS and other databases to identify male relatives. The DNA profile of an immediate family member, such as a sibling, parent or child, can provide a match that generates new leads for law enforcement. Detectives can then collect additional evidence to narrow down that new pool of individuals to a single suspect.

Last May I wrote a blog featuring a Q & A about FS provided by Mr. Rockne Harmon, a respected member of the forensic community and passionate advocate for FS. Supporters, like Harmon, and opponents agree that this method of obtaining matches to DNA evidence has demonstrated scientific precision and successful outcomes, as in the Klass case. However, it is still considered controversial and most states have not implemented specific policies regarding the application of FS to criminal investigations. So why isn’t the use of FS more widespread?

Continue reading “Familial Searching Solves Cold Cases—At What Cost?”

Did Dinosaurs Take Too Long to Hatch?

Posted on by Darcia Schweitzer

A different approach to dinosaur embryology has revealed another layer to our understanding of the demise of dinosaurs and rise of mammals as a result of the end-Cretaceous mass extinction event. In a 2017 Proceedings of the National Academy of Sciences paper, a group of researchers led by Gregory Erickson hypothesized that dinosaur eggs may have growth lines present on embryonic teeth that could be used to determine incubation times.

dinosaur-embryo

Not much is understood about dinosaur embryology, aside from what is known about birds. This is in part because fossils of dinosaur eggs, especially those containing embryonic skeletons, are among the rarest in the world. Despite this difficulty, using these fossils to refine estimated incubation times of dinosaur embryos can shed light on their development, life history and evolution.

Historically, paleontologists have assumed that dinosaur incubation periods were rapid based on their extant counterparts, birds. Considered living dinosaurs, birds are a logical surrogate from which to extrapolate dinosaur incubation times. It is important to note that embryonic incubation in birds is different from other living relatives of dinosaurs, modern reptiles. While reptile embryos develop slowly, birds differ by laying fewer, larger eggs with rapid incubation.

Continue reading “Did Dinosaurs Take Too Long to Hatch?”

Shining Light on a Superbug: Clostridium difficile

Posted on by Darcia Schweitzer

Antibiotic-resistant bacteria and their potential to cause epidemics with no viable treatment options have been in the news a lot. These “superbugs,” which have acquired genes giving them resistance to common and so-called “last resort” antibiotics, are a huge concern as effective treatment options dwindle. Less attention has been given to an infection that is not just impervious to antibiotics, but is actually enabled by them.

33553646_l

Clostridium difficile Infection (CDI) is one of the most common healthcare-associated infections and a significant global healthcare problem. Clostridium difficile (C. diff), a Gram-positive anaerobic bacterium, is the source of the infection. C. diff spores are very resilient to environmental stressors, such as pH, temperature and even antibiotics, and can be found pretty much everywhere around us, including on most of the food we eat. Ingesting the spores does not usually lead to infection inside the body without also being exposed to antibiotics.

Individuals taking antibiotics are 7-10 times more likely to acquire a CDI. Antibiotics disrupt the normal flora of the intestine, allowing C. diff to compete for resources and flourish. Once exposed to the anaerobic conditions of the human gut, these spores germinate into active cells that embed into the tissue lining the colon. The bacteria are then able to produce the toxins that can cause disease and result in severe damage, or even death.

Continue reading “Shining Light on a Superbug: Clostridium difficile”

A Crash Course in CRISPR

Posted on by Darcia Schweitzer

CRISPR is a hot topic right now, and rightly so—it is revolutionizing research that relies on editing genes. But what exactly is CRISPR? How does it work? Why is everyone so interested in using it? Today’s blog is a beginner’s guide on how CRISPR works with an overview of some new applications of this technology for those familiar with CRISPR.

Introduction to CRISPR/Cas9

27850283-June-13-CRISPR-image-WEB

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) were discovered in 1987, but it took 30 years before scientists identified their function. CRISPRs are a special kind of repeating DNA sequence that bacteria have as part of their “immune” system against invading nucleic acids from viruses and other bacteria. Over time, the genetic material from these invaders can be incorporated into the bacterial genome as a CRISPR and used to target specific sequences found in foreign genomes.

CRISPRs are part of a system within a bacterium that requires a nuclease (e.g. Cas9), a single guide RNA (sgRNA) and a tracrRNA. The tracrRNA recruits Cas9, while sgRNA binds to Cas9 and guides it to the corresponding DNA sequence of the invading genome. Cas9 then cuts the DNA, creating a double-stranded break that disables its function. Bacteria use a Protospacer Adjacent Motif, or PAM, sequence near the target sequence to distinguish between self and non-self and protect their own DNA.

While this system is an effective method of protection for bacteria, CRISPR/Cas9 has been manipulated in order to perform gene editing in a lab (click here for a video about CRISPR). First, the tracrRNA and sgRNA are combined into a single molecule. Then the sequence of the guide portion of this RNA is changed to match the target sequence. Using this engineered sgRNA along with Cas9 will result in a double-stranded break (DSB) in the target DNA sequence, provided the target sequence is adjacent to a compatible PAM sequence.

Continue reading “A Crash Course in CRISPR”

Familial DNA Searching for Criminal Forensics: Q&A

Posted on by Darcia Schweitzer

When DNA evidence is collected at a crime scene, submitting the sample for a search within a DNA database does not always identify a profile match. There is a way to extend that search and generate leads, called familial searching (FS). FS is used to identify close biological relatives of an unidentified DNA profile obtained as evidence. The basic premise is that DNA profiles of immediate family members, such as siblings, parents, or children, are likely to have more alleles in common than unrelated individuals. These familial profile matches can generate new investigative leads for law enforcement.

Currently, a few states are using FS under their state database laws, although none explicitly permit FS. Many agencies have yet to adopt policies related to FS, even though it has been found to be as effective as CODIS for identifying sources of evidence. The absence of clear ethical guidelines and policy regarding how to properly utilize FS prevents many local and state jurisdictions from adopting this investigational tool.

In order to address concerns and existing policies related to FS and to guide policy decisions by agencies implementing FS, the National Institute of Justice (NIJ) issued the report Familial DNA Searching: Current Approaches in January 2015. The goal of the report was to provide information to policy makers, law enforcement officials, forensic laboratory practitioners, and legal professionals about how FS is being applied within the criminal justice realm.

Mr. Rock Harmon, former prosecutor
Mr. Rockne Harmon, former prosecutor

Answers to the following questions about FS were provided by Mr. Rockne Harmon, a retired former prosecutor and member of the team that produced the report for the National Institute of Justice.

What is familial DNA searching?

Familial searching (FS) is an additional search of a DNA profile in a law enforcement DNA database that is conducted after a routine search fails to identify any profile matches. The FS process attempts to provide investigative leads to agencies engaged in the pursuit of justice by identifying a close biological relative of the source of the unknown forensic profile obtained from crime scene evidence.

Continue reading “Familial DNA Searching for Criminal Forensics: Q&A”