Category Archives: DNA

June 12, 2017 Scientists have known for decades that smoking cigarettes causes DNA damage, which leads to lung cancer. Now, for the first time, UNC School of Medicine scientists created a method for effectively mapping that DNA damage at high resolution across the genome. Credit: Christ-claude Mowandza-ndinga (UNC Health Care) Scientists have known for decades that smoking cigarettes causes DNA damage, which leads to lung cancer. Now, for the first time, UNC School of Medicine scientists created a method for effectively mapping that DNA damage at high resolution across the genome. The innovation comes from the laboratory of Nobel laureate Aziz Sancar, MD, PhD, the Sarah Graham Kenan Professor of Biochemistry and Biophysics at UNC's School of Medicine. In a study published in the Proceedings of the National Academy of Sciences, Sancar and his team developed a useful technique for mapping sites on the genome that are undergoing repair following a common type of DNA damage. They then used that technique to map all damage caused by the major chemical carcinogen - benzo[]pyrene. "This is a carcinogen that accounts for about 30 percent of the cancer deaths in the United States, and we now have a genome-wide map of the … Continue reading →

It has been well documented that mutations in proteins of the DNA mismatch repair (MMR) pathway underlie a variety of cancers. This genetic proofreading pathway helps to maintain genomic stability by rectifying post-replication errors that often arise between DNA base pairs. This repair pathway is so influential for cells' genetic fidelity that three investigators won the 2015 Nobel Prize in Chemistry for their groundbreaking work to understand the molecular mechanisms that control this pathway. Now, a team of scientists at the Johns Hopkins BloombergKimmel Institute for Cancer Immunotherapy and other institutions has just reported on their findings of an expanded, three-year clinical trial of 86 patients with colorectal and 11 other kinds of cancer that have MMR genetic defects. The investigators found that half of the patients responded to an immunotherapy drug called pembrolizumab (Keytruda)a programmed cell death protein 1 (PD-1) receptor inhibitorand that patient immune responses closely aligned with mutations found in their cancers. Findings from the study were published recently in Science in an article entitled Mismatch-Repair Deficiency Predicts Response of Solid Tumors to PD-1 Blockade. "Our study results may lead to a new standard-of-care that includes MMR deficiency testing to help identify a wider group of patients … Continue reading →

WABASHA A DNA match from a sexual encounter last summer resulted in criminal charges against a Zumbrota man. Cole Alexander Muenkel, 21, will make his initial appearance June 21 in Wabasha County District Court, where he faces one count each of first-, second- and third-degree criminal sexual conduct. All are felonies. He remains free in lieu of $25,000 conditional bail. The charges stem from an alleged incident Aug. 7 at an underage drinking party. A girl at the party passed out on the tailgate of a truck, the complaint says, and someone took a photo of her with several males around her, including Muenkel. He can be seen holding a canned beverage in his hand; the victim said Muenkel gave her alcohol to drink, the document says. The girl woke up in the back seat of the truck some time later to find Muenkel on top of her, sexually assaulting her, court documents say. He eventually left the back seat; after a few minutes, he came back, picked the girl up and moved her to her car, the report says. The teenager went with her mother to the hospital, where a sex assault kit and exam were completed. The victim … Continue reading →

DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a persons body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA). The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences. DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule and a phosphate molecule. Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a … Continue reading →

In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. This process occurs in all living organisms and is the basis for biological inheritance. DNA is made up of a double helix of two complementary strands. During replication, these strands are separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart, a process referred to as semiconservative replication. Cellular proofreading and error-checking mechanisms ensure near perfect fidelity for DNA replication.[1][2] In a cell, DNA replication begins at specific locations, or origins of replication, in the genome.[3] Unwinding of DNA at the origin and synthesis of new strands results in replication forks growing bi-directionally from the origin. A number of proteins are associated with the replication fork to help in the initiation and continuation of DNA synthesis. Most prominently, DNA polymerase synthesizes the new strands by adding nucleotides that complement each (template) strand. DNA replication occurs during the S-stage of interphase. DNA replication can also be performed in vitro (artificially, outside a cell). DNA polymerases isolated from cells and artificial DNA primers can be used to initiate DNA synthesis at known … Continue reading →

On this page find: Forensic science is the application of sciences such as physics, chemistry, biology, computer science and engineering to matters of law. Forensic science can help investigators understand how blood spatter patterns occur (physics), learn the composition and source of evidence such as drugs and trace materials (chemistry) or determine the identity of an unknown suspect (biology). Forensic science plays a vital role in the criminal justice system by providing scientifically based information through the analysis of physical evidence. During an investigation, evidence is collected at a crime scene or from a person, analyzed in a crime laboratory and then the results presented in court. Each crime scene is unique, and each case presents its own challenges. NIJ supports research and develop in the following forensic science disciplines: Learn about NIJs forensic science research priorities. NIJs forensic science research and development program focuses on basic and applied scientific research with the intent to: Expand the text below to see examples of scientific issues addressed by forensic science research and development. Pattern and Impression Evidence: Quantifying qualitative comparisons [Read more...] The issue: Forensic analysis of impression and pattern evidence (e.g., latent fingerprints, firearms, shoe prints, blood patterns) has traditionally … Continue reading →

In molecular biology, the term double helix[1] refers to the structure formed by double-stranded molecules of nucleic acids such as DNA. The double helical structure of a nucleic acid complex arises as a consequence of its secondary structure, and is a fundamental component in determining its tertiary structure. The term entered popular culture with the publication in 1968 of The Double Helix: A Personal Account of the Discovery of the Structure of DNA, by James Watson. The DNA double helix polymer of nucleic acid, held together by nucleotides which base pair together.[2] In B-DNA, the most common double helical structure found in nature, the double helix is right-handed with about 1010.5 base pairs per turn.[3] This translates into about 20-21 nucleotides per turn. The double helix structure of DNA contains a major groove and minor groove. In B-DNA the major groove is wider than the minor groove.[2] Given the difference in widths of the major groove and minor groove, many proteins which bind to B-DNA do so through the wider major groove.[4] The double-helix model of DNA structure was first published in the journal Nature by James Watson and Francis Crick in 1953,[5] (X,Y,Z coordinates in 1954[6]) based upon the … Continue reading →

Consuming a pack of cigarettes every day for a year can cause multiple changes in cells within various parts of the body, according to the study, published in the journal Science on Thursday. The cells in parts of the body that are directly exposed to smoke are particularly damaged, with 150 mutations found to occur in lung cells within one year, 97 in the larynx and 39 in the oral cavity. "Tobacco smoking damages DNA in organs directly exposed to smoke as well as speeds up a mutational cellular clock in organs that are both directly and indirectly exposed to smoke." said Ludmil Alexandrov of the Los Alamos National Laboratory in Los Alamos, New Mexico, who led the study. In other words, it accelerates the occurrence of genetic mutations, increasing the risk of cancer. "Before now, we had a large body of epidemiological evidence linking smoking with cancer, but now we can actually observe and quantify the molecular changes in the DNA due to cigarette smoking," Alexandrov said. Tobacco smoke is a mixture of chemicals, of which 60 are known to be carcinogens thought to cause cancer by aiding the occurrence of mutations within genes. With an increased number of … Continue reading →

DNA sequencing is the process of determining the precise order of nucleotides within a DNA molecule. It includes any method or technology that is used to determine the order of the four basesadenine, guanine, cytosine, and thyminein a strand of DNA. The advent of rapid DNA sequencing methods has greatly accelerated biological and medical research and discovery. Knowledge of DNA sequences has become indispensable for basic biological research, and in numerous applied fields such as medical diagnosis, biotechnology, forensic biology, virology and biological systematics. The rapid speed of sequencing attained with modern DNA sequencing technology has been instrumental in the sequencing of complete DNA sequences, or genomes of numerous types and species of life, including the human genome and other complete DNA sequences of many animal, plant, and microbial species. The first DNA sequences were obtained in the early 1970s by academic researchers using laborious methods based on two-dimensional chromatography. Following the development of fluorescence-based sequencing methods with a DNA sequencer,[1] DNA sequencing has become easier and orders of magnitude faster.[2] DNA sequencing may be used to determine the sequence of individual genes, larger genetic regions (i.e. clusters of genes or operons), full chromosomes or entire genomes, of any organism. … Continue reading →

Genes are the blueprints of life. Genes control everything from hair color to blood sugar by telling cells which proteins to make, how much, when, and where. Genes exist in most cells. Inside a cell is a long strand of the chemical DNA (deoxyribonucleic acid). A DNA sequence is a specific lineup of chemical base pairs along its strand. The part of DNA that determines what protein to produce and when, is called a gene. First established in 1985 by Sir Alec Jeffreys, DNA testing has become an increasingly popular method of identification and research. The applications of DNA testing, or DNA fingerprinting within forensic science is often what most people think of when they hear the phrase. Popularized by television and cinema, using DNA to match blood, hair or saliva to criminals is one purpose of testing DNA. It is also frequently used for other benefits, like wildlife studies, paternity testing, body identification, and in studies pertaining to human dispersion. While most aspects of DNA are identical in samples from all human beings, concentrating on identifying patterns called microsatellites reveals qualities specific and unique to the individual. During the early stages of this science, a DNA test was performed … Continue reading →