Dna

The coiled molecules of DNA in human cells carry a unique chemical code that can match a trace of blood, semen, skin or hair to the person who left it. DNA (deoxyribonucleic acid) carries its code in four characters denoted by the letters A,T, C, and G. But no microscope is powerful enough to see how this code is arranged on a given DNA molecule, so science must use more indirect methods to read it. Forensics laboratories use several different methods for determining whether two samples indeed carry identical stretches of code.

They seemed unlikely candidates to make one of the pivotal discoveries of the 20th century. Francis H.C. Crick was a 35-year-old Ph.D. candidate who had abandoned physics, hoping to find his niche in biology. James D. Watson was a gawky-looking 24-year-old who rarely bothered to tie his shoelaces. Both scientists were supposed to be working on other things, but they believed fervently that the most important scientific problem of their time was the mystery of inheritance - how everything from diseases to hair color to the very instructions to make a human being was passed on from generation to generation.

A man arrested recently in Puerto Rico for domestic offenses resembles the composite of the Fairmount Park rapist, city police said yesterday, adding that the suspect has lived in Philadelphia. As a result, the man, whose name was not released, has agreed to provide DNA that will be compared with evidence collected in the murder and rape of medical student Rebecca Park in Fairmount Park and the rape of another woman off Kelly Drive. The Fairmount Park assailant is also suspected of a third attack on the West River Drive in which the victim managed to fight off her attacker.

Do you have the feeling you're related to someone famous? Maybe it's an uncanny sense that Mozart was your ancestor. Or that Genghis Khan might be in your family tree. That affinity you feel for ancient Rome can't be an accident, can it? Touring the toppled ruins of columns and friezes in the ancient city stirs something in you. Perhaps one or your ancestors was one of those emperors, or perhaps just a Roman soldier. It's in your blood. Now, with a simple swab of your cheek and a few hundred dollars, you can find out. Commercial genetic genealogy is barely five years old, but already it is proving irresistible to many.

POLICE yesterday announced the arrest of a man who allegedly raped a 40-year-old woman outside the Linc during an Oct. 5, 2008, Eagles-Redskins game. "It was obviously a real challenge for us because of the number of people in and around that stadium," Special Victims Unit Capt. John Darby said yesterday. "It's almost like finding a needle in a haystack. " Police said they arrested Tiaghgee Daughtry, 22, who lives in Tunkhannock, Pa., near Scranton, on Wednesday, for allegedly raping the woman on a bus during the game.

No one really knows what happened to Phil Purcell's plane that day in September 1963 over Kontum, Vietnam. A relief pilot saw him turn his ancient B-26 back toward Da Nang. But he never arrived - plunging, instead, into the highlands below and vanishing beneath the oncoming tide of history. For three decades, as his bones and those of his crewmates moldered in Vietnam, as his children grew up and his wife remarried, the story of who he was lay locked in his body's DNA, like a song waiting to be heard.

Why do visions of war and hacked, stub-limbed civilians from Africa fail to move us as much as the images of civilians under attack in other parts of the world? I contend that we - whites, blacks and blends - are less moved by images from Africa because we've lost the emotional connection with the branch of the African human family tree. Geneticists recently have published results that say we all share the same DNA with slight variations based on traumas and the places we've passed through, via our ancestors.

For 41 years, the boy in the box has rested in his pauper's grave - unidentified, his murder unsolved. Yesterday, in a final attempt to find his killer, police removed him from his solitary grave in a potter's field in Northeast Philadelphia. They took his body to the medical examiner's office, where technicians will try to extract DNA from his remains. They hope such evidence will help identify him and eventually help nail his killer. "It's hard but it's been done before," said Lt. Ken Coluzzi, head of the special investigations unit at the police Homicide Division.

Investigators now believe murdered suburban athlete Aimee Willard was sexually assaulted. Preliminary lab tests found semen, but no evidence of the sexual trauma, sources said yesterday. Still, based on interviews with Willard's friends and family, investigators do not believe she had consensual sex, sources said. Willard, 22, of Brookhaven, Delaware County, was a senior at George Mason University in Fairfax, Va., where she played lacrosse. She was beaten to death June 20, and her body was dumped in a vacant lot in North Philadelphia.

A relative of a boy who disappeared in 1972 from an orphanage outing in Burlington County has come forward to help investigators solve the cold case. It is the latest development in a 41-year-old mystery that has inspired a network of law enforcement officers using the latest technology to find Steven Soden, then 16, and his friend, Donald Caldwell, 12. This week, authorities announced that DNA samples from four bones found with a sneaker at Bass River State Park matched DNA from Soden's relatives.

Bones found in the Pine Barrens in 2000 have been identified as belonging to a 16-year-old boy who disappeared with another youth during an orphanage camping trip in 1972, state police said Tuesday. The determination that the bones are those of Steven Soden has prompted a new search for information about his still missing companion and the Paterson orphanage from which they came. According to state police, Soden and Donald Caldwell, 12, disappeared the night of April 3, 1972, while on a weeklong outing to Bass River State Park in Burlington County.

Before he walked into an honors communications course at West Chester University, Grant Hubbard's ethnic identity was the stuff of skin color and oral history. He was the white guy with European roots whose family came to the United States shortly after the Mayflower arrived. Then science took over. The swipe of a cotton swab inside his cheek and a DNA test indicated that he had ancestors from Europe, and elsewhere. "My results came back 60 percent Southeast Asian," said Hubbard, 20, of Downingtown.

OXFORD, Miss. - A dust mask that tested positive for ricin also contained DNA from a Mississippi man suspected of sending poison-laced letters to President Obama and others, an FBI agent testified Thursday. The testimony came during a preliminary hearing for James Everett Dutschke, 41, who was arrested Saturday at his home in Tupelo and charged with making ricin, the same substance mailed on April 8 to Obama, U.S. Sen. Roger Wicker, and Mississippi Judge Sadie Holland. Magistrate Judge S. Allan Alexander ruled that there was enough probable cause to send the case to a grand jury.

Jerrold Meinwald is one of the founding fathers of a field called chemical ecology, often speaking in large lecture halls about how insects and other animals repel predators with toxins. On Tuesday at the Franklin Institute, he had to defend his life's work in a less-formal setting - face-to-face with inquisitive high-schoolers. How are the toxins made? students asked. How concentrated are they? Which creatures emit the most toxic poisons? "You have to ask, 'Poisonous to whom?

EVERY DAY for the last 17 years, a desolate stretch of Hope Street has haunted Paulette Smith as she passed high above the North Philadelphia block during her commute to work on the El. It was on that gray, litter-clogged block near Montgomery Avenue where her teenage daughter's battered, lifeless body was found inside an abandoned house in October 1996, two days after a stranger had snatched her off the street only steps away from the safety of...

Two men spent more than a decade behind bars before DNA evidence exonerated them. After their release, one married, held a steady job, and earned a pension. The other is on welfare and lives with his mother. What separates their situations? Mainly, a river. While individual traits and circumstances surely played a role in the former inmates' differing destinies, prison reform advocates say it was crucial that one received a hand up from the state upon release and the other did not. Since 1997, New Jersey has compensated the wrongfully convicted with at least $20,000 for each year of incarceration.

The scientist and his companions puttered down winding waterways by boat, and bounced along dirt roads in a Ford Explorer. The longest of more than a dozen such trips into the Malaysian jungle took 10 hours. Only then could the researcher from Penn State College of Medicine ask tribal leaders for the information he sought: Surat warisan manusia . The letter of human inheritance. That was Khai C. Ang's way of explaining the concept of DNA, and it was effective. Hundreds of villagers agreed to give blood samples, and now back in the Hershey, Pa., lab of Ang's supervisor, Keith Cheng, their DNA has begun to yield insight into a weighty trio of subjects: cancer, human migration, and race.

Human genes seem to be activated by stretches of DNA found in between the genes but not very close to them. Each activator is often located thousands of base pairs away from its corresponding gene, so scientists have been puzzled as to just how they get the job done. Researchers at Wistar Institute reported on Sunday that they had found part of the answer: At the appropriate moment, each gene and its activator come together as if the DNA were string being tied into a loop. The findings help to explain what occurs during embryonic development, when the pinpoint timing of gene activation plays a role in whether a cell becomes part of, say, a liver or a heart, and even whether the organism is a human or another species.