Category Archives: DNA

Selangor Police Chief Abdul Samah Mat said without DNA from a next of kin, they won't hand over Kim Jong Nam's body or release the autopsy report, which could reveal the cause of death.

But North Korea says it will "reject" the results of a "forced" autopsy which was not witnessed by its officials, according to a statement from the country's ambassador to Malaysia, Kang Chol. The ambassador demanded the immediate release of the body.

Kim Jong Nam died after being attacked at Kuala Lumpur International Airport on Monday. South Korean officials claim he was poisoned.

Three people have been arrested so far in relation to Kim's murder: an Indonesian woman, a Malaysian man and another woman carrying Vietnamese identification.

Four days after the killing, many questions remain unanswered. Here's what we know so far.

Kim was on his way to catch a flight Monday morning to see his family in Macau, where he's lived since his departure from North Korea years ago.

The Chinese territory, a short ferry or helicopter ride from Hong Kong, is a popular gambling destination with mainland Chinese.

The exact details of Kim's murder are sketchy but Selangor State Criminal Investigations Department Chief Fadzil Ahmat told Reuters Kim "felt like someone grabbed or held his face from behind."

Kim felt dizzy and immediately went to an airport customer assistance counter, seeking medical help. They were concerned enough to take him to the on-premises clinic.

An ambulance was called to take Kim to the hospital, but he died on the way.

No one is exactly sure how Kim died.

Initially, local media put forth reports of poison needles and deadly sprays, but it wasn't even clear whether Kim was killed or had a heart attack.

Then on Wednesday, South Korea's Lee Cheol Woo, the chairman of the country's National Assembly Intelligence Committee, publicly declared Kim had been murdered.

The autopsy may have revealed more, but despite having been finished on Wednesday, no results have been released.

As of yet, Deputy Prime Minister Hamidi said no next of kin had come forward to claim the body.

No motive for the killing has been revealed, nor any explanation of how he was poisoned.

South Korea's Lee told lawmakers on Wednesday that North Korea killed Kim but, again, he didn't explain how he knew it.

"Pyongyang has been attempting to assassinate Kim Jong Nam for the past five years," a South Korean legislator, Lee Chul Woo, told reporters Wednesday. He didn't provide any evidence.

When asked about rumors that North Korea had been involved in Kim's death, Malaysian Deputy Prime Minister Ahmad Zahid Hamidi told a press conference Thursday it was "only speculation."

North Korea has requested Kim's body, but Malaysian authorities said they wouldn't release it until investigations are complete. The North Korean ambassador's statement said Malaysia initially told consular officials that Kim died of a heart attack on the way to a hospital.

North Korea accused Malaysia of "collusion with the hostile forces towards our government."

Grainy security video from the airport at the time of Kim's killing showed two young female suspects. One of the women is seen wearing a blue skirt and white t-shirt with "LOL" written on it.

The first woman was arrested on Wednesday morning at Kuala Lumpur International Airport, two days after the attack. She was carrying Vietnamese documents, which said her name was Doan Thi Huong and gave her age as 30.

Later that evening, 26-year-old Malaysian Muhammad Farid Bin Jalaluddin was taken into custody. Police said he was arrested to assist in their investigations.

At 2 a.m. on Thursday, Jalaluddin led investigators to his girlfriend, 25-year-old Indonesian Siti Aishah, who was then arrested on suspicion of being involved in Kim's death. No charges have been laid.

Born in 1971, he was the first son of then-North Korean leader Kim Jong Il.

His mother was one of the dictator's favored mistresses, actress Song Hye-rim, and for a while Kim Jong Nam was the most public of his father's sons.

But in 2001 he reportedly lost the elder Kim's favor when he tried to use forged documents to visit Tokyo Disneyland.

His half-brother, Kim Jong Un, was born to a different mistress, Ko Yong Hui, who was politically ambitious and enthusiastic to see her son succeed his father as leader.

But author Yoji Gomi, who wrote a book in 2012 called "My Father, Kim Jong Il, and Me" said Kim Jong Nam thought his younger brother wasn't fit to run the country.

CNN's Andreena Narayan, Sandi Sidhu and journalist KL Chan contributed to this report.

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Give us Kim family's DNA or no body, Malaysian police tell North Korea - CNN

On Aug. 8, 1998, a 38-year-old woman was left on the side of a residential road offU.S. 278 outside Avondale Estates. Monica Faye Blackwell had been raped and killed, and the assailant was gone.

Now the man accused is in the DeKalb County jail. Samuel McCullum, 52, was connected to Blackwells death by DNA after his 2002 unlawful imprisonment of a 17-year-old girl in Kentucky, according to the DeKalb DAs office.

McCullum was extradited to Georgia last week after completinghis sentence in Kentucky. He faces charges of rape and murder in Blackwells death and is also awaiting trial in another local rape, the DAs office said.

Warrants released this week to The Atlanta Journal-Constitution dont specify how McCullum is accused of killing Blackwell. But the documents say he killed her and dumped her on the side of Porter Road at about 11 p.m.

The DAs office declined to release further information on the case.

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DNA hit spurs arrest in 1998 rape, killing of woman in DeKalb - Atlanta Journal Constitution

February 17, 2017 A powerful Northwestern University imaging tool is the first to measure the structure of isolated chromosomes without the use of fluorescent labels. Credit: Northwestern University

Many of the secrets of cancer and other diseases lie in the cell's nucleus. But getting way down to that levelto see and investigate the important genetic material housed thererequires creative thinking and extremely powerful imaging techniques.

Vadim Backman and Hao Zhang, nanoscale imaging experts at Northwestern University, have developed a new imaging technology that is the first to see DNA "blink," or fluoresce. The tool enables the researchers to study individual biomolecules as well as important global patterns of gene expression, which could yield insights into cancer.

Backman will discuss the tool and its applicationsincluding the new concept of macrogenomics, a technology that aims to regulate the global patterns of gene expression without gene editingFriday (Feb. 17) at the American Association for the Advancement of Science (AAAS) annual meeting in Boston.

The talk, "Label-Free Super-Resolution Imaging of Chromatin Structure and Dynamics," is part of the symposium "Optical Nanoscale Imaging: Unraveling the Chromatin Structure-Function Relationship," which will be held from 1 to 2:30 p.m. Eastern Time Feb. 17 in Room 206, Hynes Convention Center.

The Northwestern tool features six-nanometer resolution and is the first to break the 10-nanometer resolution threshold. It can image DNA, chromatin and proteins in cells in their native states, without the need for labels.

For decades, textbooks have stated that macromolecules within living cells, such as DNA, RNA and proteins, do not have visible fluorescence on their own.

"People have overlooked this natural effect because they didn't question conventional wisdom," said Backman, the Walter Dill Professor of Biomedical Engineering in the McCormick School of Engineering. "With our super-resolution imaging, we found that DNA and other biomolecules do fluoresce, but only for a very short time. Then they rest for a very long time, in a 'dark' state. The natural fluorescence was beautiful to see."

Backman, Zhang and collaborators now are using the label-free technique to study chromatinthe bundle of genetic material in the cell nucleusto see how it is organized. Zhang is an associate professor of biomedical engineering at McCormick.

"Insights into the workings of the chromatin folding code, which regulates patterns of gene expression, will help us better understand cancer and its ability to adapt to changing environments," Backman said. "Cancer is not a single-gene disease."

Current technology for imaging DNA and other genetic material relies on special fluorescent dyes to enhance contrast when macromolecules are imaged. These dyes may perturb cell function, and some eventually kill the cellsundesirable effects in scientific studies.

In contrast, the Northwestern technique, called spectroscopic intrinsic-contrast photon-localization optical nanoscopy (SICLON), allows researchers to study biomolecules in their natural environment, without the need for these fluorescent labels.

Backman, Zhang and Cheng Sun, an associate professor of mechanical engineering at McCormick, discovered that when illuminated with visible light, the biomolecules get excited and light up well enough to be imaged without fluorescent stains. When excited with the right wavelength, the biomolecules even light up better than they would with the best, most powerful fluorescent labels.

"Our technology will allow us and the broader research community to push the boundaries of nanoscopic imaging and molecular biology even further," Backman said.

Explore further: Researchers discover that DNA naturally fluoresces

A Northwestern University team recently caught DNA doing something that has never been seen before: it blinked.

When scientists finished decoding the human genome in 2003, they thought the findings would help us better understand diseases, discover genetic mutations linked to cancer, and lead to the design of smarter medicine. Now ...

In 2014, an international trio won the Nobel Prize in Chemistry for developing super-resolution fluorescence microscopy, a technique that made it possible to study molecular processes in living cells.

Researchers at The University of Nottingham have developed a break-through technique that uses sound rather than light to see inside live cells, with potential application in stem-cell transplants and cancer diagnosis.

Imaging very small materials takes not only great skill on the part of the microscopist, but also great instruments and techniques. For a refined microscopic look at biological materials, the challenges include getting an ...

A team led by a Northwestern University biomedical engineer has developed a new optical technique that holds promise for minimally invasive screening methods for the early diagnosis of cancer.

Hens that do not produce their own chicks have been developed for use as surrogates to lay eggs from rare breeds.

Many of the secrets of cancer and other diseases lie in the cell's nucleus. But getting way down to that levelto see and investigate the important genetic material housed thererequires creative thinking and extremely ...

Climate change from political and ecological standpoints is a constant in the media and with good reason, said a Texas A&M AgriLife Research scientist, but proof of its impact is sometimes found in unlikely places.

New DNA-based research provides compelling evidence that a group of strange-looking fish living near the mouth of the Congo River are evolving due to the intense hydraulics of the river's rapids and deep canyons. The study, ...

New research involving Monash University biologists has debunked the view thatmalesjust pass on genetic materialand not much else to their offspring. Instead, it found a father's diet can affect their son's ability ...

At what point on the journey along the branches of the evolutionary tree does a population become its own, unique species? And is a species still distinct, if it mates with a different, but closely related species? Evolutionary ...

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Researchers are first to see DNA 'blink' - Phys.org - Phys.Org

A couple of new studies reveal that salmonella may have been the cause of mass devastation to the Aztec civilization, at least according to the DNA of bacterium pulled from burial locations in Mexico. The nations native inhabitants were hit with a severe pestilence of some sort, one powerful enough to have wiped out as much as 80-percent of the population. The exact cause of that devastation has been a source of mystery.

The decimation of Mexicos native population followed the arrival of European colonization. In the early 1500s, just before Spanish conquistadors arrived, there were about 25 million individuals in the region. Only 100 years later, and due in part to the epidemic, only about a million individuals in the native population remained.

It was one of the worst recorded epidemics ever, and it happened in two batches, one in 1545 and another 1576. A big mystery has surrounded the pathogen behind the epidemic, though some diseases like smallpox have since been ruled out. Now we may finally have the answer thanks to bacterium harvested from the teeth of individuals buried in Southern Mexico, with the graves dating back to the relevant time period.

The DNA of this bacteria is linked to salmonella, particularly a strain called Paratyphi C that is commonly found in developing nations. When infected with this salmonella, victims develop a condition called enteric fever which, if not treated, will kill between 10 and 15-percent of afflicted individuals.

SOURCE: Nature

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Bacterial DNA reveals salmonella may have wiped out the Aztecs - SlashGear

February 17, 2017 Transcripts from the ASCC3 gene are found in two different cellular compartments. The long mRNA isoform (left) is predominantly cytoplasmic, while the short non-coding RNA (ncRNA, right) is in the cell nucleus (blue). Credit: The Francis Crick Institute

It's well known that when the DNA in a cell is damaged, the cell responds by activating specific genes that help defend the integrity of its genome. But less well studied is the fact that the cell actually shuts down the vast majority of its other genes.

For the first time, scientists at the Francis Crick Institute have analysed this phenomenon at the molecular level. They found that transcription of all genes slows rapidly and dramatically in response to DNA damage. They also discovered an example of a gene where a shorter non-coding version was transcribed because of this slowdown, and via so-called alternative splicing. This non-coding RNA then helps the cell to survive the DNA damage.

The importance of alternative splicing remains a matter of debate; while it was previously presumed that the process helps create great complexity in protein function from a limited number of genes, some researchers have recently insisted that alternative splicing cannot be important since proteomic analysis has shown that most genes only have a single protein form, implying that most alternative gene transcripts do not have a function.

The functional example of alternative splicing the Crick scientists describe is a gene called ASCC3. ASCC3 usually codes for a protein, but when there is DNA damage and gene transcription slows down, a much shorter RNA molecule is transcribed from the same gene instead. Remarkably, this form does not code for a protein so is known as a non-coding RNA. The researchers discovered that in fact, this alternative non-coding RNA is a stable transcript found in the cell's nucleus that plays a role in counteracting the original protein coded by the same gene.

Jesper Svejstrup, who led the work, says: "There may be many other genes like this; we certainly know there are scores of genes that appear to behave similarly in the DNA damage response. Such alternative non-coding RNA transcripts may also be up-regulated in response to other kinds of cellular stress. Indeed, many, many genes in the genome express short RNA forms that are almost always ignored because it makes no sense that they could code for proteins.

"Now that we know that BOTH a protein-coding and an alternative non-coding but functionally important RNA can be expressed from the same gene, researchers will start looking for functions for their short and potentially non-coding RNA transcripts in whatever physiological system they are working. Our work also illustrates the potential physiological relevance and relevance to disease of such unstudied transcripts."

The paper, UV-Irradiation Induces a Noncoding RNA that Functionally Opposes the Protein Encoded by the Same Gene, is published in Cell.

Explore further: 'Mysterious' non-protein-coding RNAs play important roles in gene expression

More information: Laura Williamson et al. UV Irradiation Induces a Non-coding RNA that Functionally Opposes the Protein Encoded by the Same Gene, Cell (2017). DOI: 10.1016/j.cell.2017.01.019

Journal reference: Cell

Provided by: The Francis Crick Institute

In cells, DNA is transcribed into RNAs that provide the molecular recipe for cells to make proteins. Most of the genome is transcribed into RNA, but only a small proportion of RNAs are actually from the protein-coding regions ...

The human genome contains some 20,000-25,000 protein-coding genes, which is surprisingly similar to the number of genes in worms and flies. Where does complexity of our organism and behaviour come from? In many genes, coding ...

While the number of coding genes that produce proteins in humans has dwindled to 20,000 in recent years, scientists think that the dimensions of the proteome could be larger. This diversity of proteins has become one of the ...

New VIB/UGent research adds an extra dimension to the known set of human proteins. Genes can shift their expression towards alternative protein versions (proteoforms) that rival their full length counterparts in stability. ...

Before RNA copies of genes can program the synthesis of proteins, the non-coding regions are removed by the spliceosome. Munich researchers report that distinct conformations of a member of this molecular complex play a vital ...

Prostate cancer researchers studying genetic variations have pinpointed 45 genes associated with disease development and progression.

Hens that do not produce their own chicks have been developed for use as surrogates to lay eggs from rare breeds.

Many of the secrets of cancer and other diseases lie in the cell's nucleus. But getting way down to that levelto see and investigate the important genetic material housed thererequires creative thinking and extremely ...

Climate change from political and ecological standpoints is a constant in the media and with good reason, said a Texas A&M AgriLife Research scientist, but proof of its impact is sometimes found in unlikely places.

New DNA-based research provides compelling evidence that a group of strange-looking fish living near the mouth of the Congo River are evolving due to the intense hydraulics of the river's rapids and deep canyons. The study, ...

New research involving Monash University biologists has debunked the view thatmalesjust pass on genetic materialand not much else to their offspring. Instead, it found a father's diet can affect their son's ability ...

At what point on the journey along the branches of the evolutionary tree does a population become its own, unique species? And is a species still distinct, if it mates with a different, but closely related species? Evolutionary ...

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What happens to gene transcription during DNA damage? - Phys.Org

Paul Srubas(Photo: USA TODAY NETWORK-Wisconsin)Buy Photo

Now, according to the TV commercial, you can have your DNA tested.

This isnt about getting away with murder. In this case at least, your DNA wont prove you didnt really kill Col.Mustard with the candlestick in the drawing room. This is only about checking out your ancestry.

Were the Great Melting Pot here in the USA, but that doesnt mean we all dont want to trace ourselves back to something really cool, whatever that is. Royalty, I suppose, or the guy who invented socks.

This test doesnt get that specific. Itjust determines where your people came from. Having a name that begins with Vander-"or ends in ski doesnt cut it anymore.

Ive got a friend who tried it. He always thought he was Irish, but the test came back saying he was Danish and Romanian. As we all know, there are two kinds of people in this world, the Irish and those who wish they were, and my friend just crossed the Great Divide going the wrong way. Now hes stuck being Danish and Romanian. They wont send him a refund.

Heres what baffles me. These guys doing the testing how do they know where to stop? I mean, people have always moved around a lot, but humanity supposedly originated in Ethiopia. If this testing company told everybody they evolved from Ethiopians, it wouldnt stay in business long.

Youre a direct descendant of Adam and Eve! Thatll be $200, please!

On the other hand, if I sent in a sample and it came back identifying my ancestry as having come from the Neenah-Menasha area, I think Id go to the police.

So this company cleverly chooses to target somewhere in between these two extremes, at some limited number of digits in the DNA sequence that takes results beyond your mom and dads home town but stops somewhere short of the Cradle of Civilization.

Um, Denmark and Romania! Thats it. Your people were from Denmark and Romania!

All they have to do is go back far enough that theres no way to check.

Someone with excess money could test their honesty, I guess. Send them two samples at two different times and see whetherthe results match. Maybe you can surprise yourself to learn youre Belgian and your twin sister is Polish.

Give it a try and let me know what you find out. Dont send them blood, though. You just have to lick the envelope. And remember to enclose a check or money order.

psrubas@pressgazettemedia.com and follow him on Twitter@PGpaulsrubas

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DNA test: Who's your daddy's daddy? - Green Bay Press Gazette

A group of international scientists opened Pandoras box this week with a new report arguing that it may be acceptable to genetically edit unborn babies DNA in certain circumstances.

According to Science magazine, the report came from an international committee organized by the U.S. National Academy of Sciences and the National Academy of Medicine in Washington, D.C.

The committee said more research needs to be done before a clinical trial could take place. It also

cautioned that DNA editing should only be done for compelling reasons and under strict oversight, according to the report it released Tuesday.

However, the new committee report is a significant deviation from previous recommendations in the scientific community that the practice is unethical and should be prohibited.

Marcy Darnovsky, executive director of the Center for Genetics and Society in Berkeley, California told the magazine: Were very disappointed with the report. Its really a pretty dramatic shift from the existing and widespread agreement globally that human germline editing should be prohibited.

Many are concerned that the practice eventually would lead to genetically modified designer babies, with parents choosing the hair and eye color, sex and other traits.

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situations could be limited to couples who both have a serious genetic disease and for whom embryo editing is really the last reasonable option if they want to have a healthy biological child, says committee co-chair Alta Charo, a bioethicist at the University of Wisconsin in Madison.

Some researchers are pleased with the report, saying it is consistent with previous conclusions that safely altering the DNA of human eggs, sperm, or early embryosknown as germline editingto create a baby could be possible eventually. They have closed the door to the vast majority of germline applications and left it open for avery small, well-defined subset. Thats not unreasonable in my opinion, says genome researcher Eric Lander of the Broad Institute in Cambridge, Massachusetts. Lander was among the organizers of an international summit at NAS in December 2015 who called for more discussion before proceeding with embryo editing.

Later, it continued:

The committees report finds that human embryo editing may be acceptable to prevent a baby from inheriting a serious genetic diseasebut only if specific safety and ethical criteria are met. For example, the couple cannot have reasonable alternatives, such as the option of selecting healthy embryos for in vitro fertilization (IVF) or using prenatal testing and aborting a fetus with the disease. One situation that could meet the reports criteria would be if both parents have the same disease, such as cystic fibrosis, that is caused by carrying two copies of a mutation, the report says. In that case, an embryo will also carry the harmful mutations.

The panel formed in response to new technology that makes it easier to edit human DNA, according to the magazine. The most well known is a DNA editing tool named CRISPR.

In 2015, pro-life bioethics author Rebecca Taylor wrote about CRISPR and its potential dangers.

It really is time for the public to realize that the genetic engineering that they see in movies is quite possibly achievable, not in our grand-childrens lifetimes, but in our own, she wrote. It is time to stop ignoring the steady advance of genetic engineering and take charge of its direction.

In the United States, this means we must get federal legislation on the books that addresses the genetic engineering of human beings, most importantly the genetic engineering of human embryos, Taylor continued. Unlike most other civilized countries in the world, we have no laws at the federal level governing the genetic manipulation of humans.

Link:
Scientists Given Green Light to Edit the DNA of Unborn Babies - LifeNews.com

Wednesdaynights Crashing premiere at the Avalon in Hollywood, was like a comedy prom as part ofJudd Apatowspack gathered to celebrate the debut of Pete Holmes wry new show. Writing what he knew, the show is about Holmes breakup with his wife after she cheated on him while he struggled to be a successful comedian. In real life, Holmes is now happily engaged.

Holmes explained why Crashing is a good fit at HBO, It reminds me of Girls in the way were trying to take the biggest shortcomings and things that make my character gross and showcasing those. Thats something Lena [Dunham] is so good at: showing things people usually hide and bringing them onscreen for comedy.

Holmes also shows how his Christian religion affected his comedy journey in the story, I liked Jerry Seinfeld, Brian Regan, Ray Romano I really liked those guys and I was trying to be one of those guys and thats really what the show is about. [My character] is really burdened because he wants to be a good boy and he wants to be clean, but when you start in the clubs of New York, you follow five or six other comedians talking about sex and their genitalia. Thats part of the struggle were trying to show.

Apatow, executive producer of the series, talked about how his continuing creative relationship with HBO and Holmes made it a great fit for him.It seemed like a sad idea for a show, but a year later [Pete] said he wanted to talk about doing a personal TV show, and thats my favorite thing. Pain is the motive for comedy. Happy people are never funny.

Among those spotted in the premiere crowd were guest stars Artie Lange, T.J. Miller, Gina Gershon, Kristen SchaalandJermaine Fowler. After the screening, guests feasted on a comedy club-inspired menu of cheeseburgers, fries, grilled cheese sandwiches, four kinds of pizza, and a cereal bar and mini Krispy Kreme doughnuts for dessert.

Crashing premieres Sunday, Feb. 19 on HBO.

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Pete Holmes: HBO's 'Crashing' Shares Some 'Girls' DNA - Variety

A man has been arrested in connection with the 2001 kidnapping and sexual assault of a 14-year-old Northridge boy after DNA evidence gathered from an unrelated arrest linked him to the cold case, the Los Angeles Police Department announced.

LAPD released this photo of Mirek Voyt who was arrested on Feb. 14, 2017 in connection with the 2001 kidnapping and sexual assault of a 14-year-old boy.

Mirek Voyt, 54, was arrested on Feb. 14 at his home in Hollywood and charged with kidnapping to commit sexual assault in connection with a crime that happened on June 22, 2001, LAPD Capt. William Hayes said at a news conference Thursday.

Police said about 9:45 a.m. that morning, two teenage boys were walking to school in the area of Vanalden Avenue and Chase Street in Northridge when they were allegedly approached by Voyt.

The suspect confronted the individuals with a handgun. One of the individuals was able to flee, but he unfortunately was able to kidnap one of the two young men who was 14, Hayes said. He took him to an undisclosed location where he sexually assaulted that young man and eventually after a period of time he released the young man.

Hayes said at the time of the crime, Voyt lived in close proximity to the school. The victim told police he had been blindfolded while he was kidnapped and sexually assaulted.

Investigators gathered evidence including a DNA profile which was uploaded into a DNA database, but no suspects met the profile at that time.

A break in the case came in late 2016 when Voyt was arrested on an unrelated grand theft charge.

Voyts DNA was put into a database as a result of his arrest, and there was a match linking him to the 2001 Northridge case involving the 14-year-old boy, Hayes said.

Hayes said investigatorsbelieve there may be more potential victims and encourage them to contact police.

Although hes remained off the radar in terms of other criminal activities, one would find it hard to believe that this was his only time, Hayes said.

Voyt was being held without bail.

Police said prior to his arrest, Voyt worked in a management position at a grocery store chain.

Anyone with information about this crime, or similar crimes, is asked to contact Det. Carla Zuniga at 213-486-6910. Anyone wishing to remain anonymous can call 800-222-8477.

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DNA From Grand Theft Arrest Links Suspect to Kidnapping and Sexual Assault of 14-Year-Old Northridge Boy in 2001 ... - KTLA

February 16, 2017 Credit: rost9 / fotolia.com

The evolution of cells and organisms is thought to have been preceded by a phase in which informational molecules like DNA could be replicated selectively. New work shows that hairpin structures make particularly effective DNA replicators.

In the metabolism of all living organisms there is a clear division of labor: Nucleic acids (DNA and RNA) carry the information for the synthesis of proteins, and proteins provide the structural and executive functions required by cells, such as the controlled and specific catalysis of chemical reactions by enzymes. However, in recent decades, it has become clear that this distinction is by no means absolute. In particular RNA is capable of ignoring the boundary outlined above and is known to play a catalytic role in many important processes. For example, certain RNA molecules can catalyze the replication of other nucleic acids, and this versatility could help to explain how life originated on Earth.

Nucleic acid molecules are made up of subunits called nucleotides, which differ in their so-called bases. The bases found in RNA are referred to as A, C, G and U (DNA uses T in place of U). These bases fall into two complementary pairs, whose members specifically interact, A with T (or U) and G with C. This complementarity is what accounts for the stability of the DNA double helix, and enables single strands of RNA to fold into complex shapes.

Life is thought to have emerged from a process of chemical evolution in which nucleic acid sequences could be selectively replicated. Thus, in prebiotic systems certain molecular "species" that carried information were reproduced at the expense of others. In biological systems, such selectivity is normally mediated by so-called primersstrands of nucleic acid that pair (as described above) with part of the molecule to be replicated, to form a short double helix. The primer provides a starting point for the extension of the double-stranded region to form a new daughter strand. Moreover, this process can be reconstructed in the test-tube.

The pros and cons of hairpin replicators

Georg Urtel and Thomas Rind, who are members of the research group led by Dieter Braun (Professor of Systems Biophysics at LMU), have used such a system to identify properties the might favor the selective replication of DNA molecules. For their experiments, they chose a single-stranded DNA sequence that adopts a so-called hairpin structure. In these molecules, the base sequences at either end are complementary to each other, as are short stretches of sequence within the rest of the molecule. This distribution of complementary sequences causes such a strand to fold into a hairpin-like conformation.

Thanks to the pairing rules outlined above, replication of a single strand of DNA produces a second strand whose sequence differs from that of the first. Each strand of a non-hairpin structure therefore needs its own primer for replication. But with hairpins, one primer suffices to prime synthesis of both the original and its complementary strand. "This means that hairpins are relatively simple replicators," Georg Urtel points out. The downside is that the hairpin structure makes primer binding more difficult, and this in turn limits their replication rate. Molecular species that are devoid of hairpin structures don't have this problem.

Cooperation beats competition

In subsequent experiments the researchers discovered that two simple hairpin species could cooperate to give rise to a much more efficient replicator, which requires two primers for its amplification. The two hairpin species selected each required a different primer, but their sequences were in part identical. The switch to cooperative replication occurs when replication of one of the hairpins stalls. "As a rule, replication processes in nature are never perfect," says Dieter Braun. "Such a premature halt is not something that one needs to design into the system. It happens stochastically and we make use of it in our experiments." The partially replicated hairpin can, however, bind to a molecule of the second species, and serves as a primer that can be further elongated. Moreover, the resulting product no longer forms a hairpin. In other words, it represents a new molecular species.

Saved from extinction

Such so-called 'crossbreeds' need two primers for their replication, but can nevertheless be replicated significantly faster than either of their hairpin progenitors For further experiments showed that, upon serial dilution of the population, the hairpin DNAs soon become extinct. However, the sequence information they contained survives in the crossbreeds and can be replicated further.

The converse experiment confirmed that information is indeed conserved: If crossbreeds are supplied with only one primer, the corresponding progenitor hairpin species can still be replicated by the kind of switching process mentioned above. But, in the absence of the second primer, the crossbreed dies out. "Thus, the crossbreeding process not only provides for the transition from 'simple and slow' replicators to more rapid replicators, it also makes it possible for the system to adapt to the prevailing conditions," Urtel explains. "It also suggests how early replicators could have cooperated with each other under prebiotic conditions prior to the origin of living systems."

Explore further: Genetic switch regulates transcription and replication in human mitochondria

More information: Georg C. Urtel et al. Reversible Switching of Cooperating Replicators, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.118.078102

(Phys.org)The majority of the human genome is located within the nucleus. However, there is a small but important portion of DNA located within the mitochondria. This mitochondrial DNA (mtDNA) has received much attention ...

Researchers at Case Western Reserve University and the University of Michigan have produced the first image of an important human protein as it binds with ribonucleic acid (RNA), a discovery that could offer clues to how ...

MIT scientists have found a new way that DNA can carry out its work that is about as surprising as discovering that a mold used to cast a metal tool can also serve as a tool itself, with two complementary shapes each showing ...

DNA lesions are really common about one million individual molecular lesions per cell per day because its long strands usually have one missing base or are damaged. These lesions can stall the DNA replication process, ...

The original recipe for gene soup may have been simplerain, a jumble of common molecules, warm sunshine, and nighttime cooling. Then add a pinch of thickener.

UV light damages DNA. But LMU researchers now show that it can also mediate non-enzymatic repair of one type of damage, albeit in a specific context. This effect may have played vital role in early evolution of living systems.

Research led by ANU on the use of magnets to steer light has opened the door to new communications systems which could be smaller, cheaper and more agile than fibre optics.

University of Toronto (U of T) researchers have demonstrated a way to increase the resolution of microscopes and telescopes beyond long-accepted limitations by tapping into previously neglected properties of light. The method ...

The demand for faster computers is growing rapidly and the rise of big data demands novel solutions be explored to deliver quicker results.

Although scientists have been able to levitate specific types of material, a pair of UChicago undergraduate physics students helped take the science to a new level.

Experiments at ANSTO have provided supporting evidence of unexpected enhancement of water solubility of biomolecules in an aqueous solution of divalent transition-metal cations.

A detection device designed and built at Yale is narrowing the search for dark matter in the form of axions, a theorized subatomic particle that may make up as much as 80% of the matter in the universe.

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Molecular hairpin structures make effective DNA replicators - Phys.Org