|
Paleogenetics
Paleogenetics is the study of the past through the examination of preserved genetic material from the remains of ancient organisms. Emile Zuckerkandl and Linus Pauling introduced the term in 1963, long before the sequencing of DNA, in reference to the possible reconstruction of the corresponding polypeptide sequences of past organisms. The first sequence of ancient DNA, isolated from a museum specimen of the extinct quagga, was published in 1984 by a team led by Allan Wilson. Paleogeneticists do not recreate actual organisms, but piece together ancient DNA sequences using various analytical methods. Fossils are "the only direct witnesses of extinct species and of evolutionary events" and finding DNA within those fossils exposes tremendously more information about these species, potentially their entire physiology and anatomy. The most ancient DNA sequence to date was reported in February 2021, from the tooth of a Siberian mammoth frozen for over a million years. Applications ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeogenetics
Archaeogenetics is the study of ancient DNA using various molecular genetic methods and DNA resources. This form of genetic analysis can be applied to human, animal, and plant specimens. Ancient DNA can be extracted from various fossilized specimens including bones, eggshells, and artificially preserved tissues in human and animal specimens. In plants, Ancient DNA can be extracted from seeds and tissue. Archaeogenetics provides us with genetic evidence of ancient population group migrations, domestication events, and plant and animal evolution. The ancient DNA cross referenced with the DNA of relative modern genetic populations allows researchers to run comparison studies that provide a more complete analysis when ancient DNA is compromised. Archaeogenetics receives its name from the Greek word ''arkhaios'', meaning "ancient", and the term ''genetics'', meaning "the study of heredity". The term archaeogenetics was conceived by archaeologist Colin Renfrew. In February 2021, scientis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient DNA
Ancient DNA (aDNA) is DNA isolated from ancient specimens. Due to degradation processes (including cross-linking, deamination and fragmentation) ancient DNA is more degraded in comparison with contemporary genetic material. Even under the best preservation conditions, there is an upper boundary of 0.4–1.5 million years for a sample to contain sufficient DNA for sequencing technologies. The oldest sample ever sequenced is estimated to be 1.65 million years old. Genetic material has been recovered from paleo/archaeological and historical skeletal material, mummified tissues, archival collections of non-frozen medical specimens, preserved plant remains, ice and from permafrost cores, marine and lake sediments and excavation dirt. On 7 December 2022, ''The New York Times'' reported that two-million year old genetic material was found in Greenland, and is currently considered the oldest DNA discovered so far. History of ancient DNA studies 1980s The first study of what would ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient DNA
Ancient DNA (aDNA) is DNA isolated from ancient specimens. Due to degradation processes (including cross-linking, deamination and fragmentation) ancient DNA is more degraded in comparison with contemporary genetic material. Even under the best preservation conditions, there is an upper boundary of 0.4–1.5 million years for a sample to contain sufficient DNA for sequencing technologies. The oldest sample ever sequenced is estimated to be 1.65 million years old. Genetic material has been recovered from paleo/archaeological and historical skeletal material, mummified tissues, archival collections of non-frozen medical specimens, preserved plant remains, ice and from permafrost cores, marine and lake sediments and excavation dirt. On 7 December 2022, ''The New York Times'' reported that two-million year old genetic material was found in Greenland, and is currently considered the oldest DNA discovered so far. History of ancient DNA studies 1980s The first study of what would ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancestral Reconstruction
Ancestral reconstruction (also known as ''Character Mapping'' or ''Character Optimization'') is the extrapolation back in time from measured characteristics of individuals (or populations) to their common ancestors. It is an important application of phylogenetics, the reconstruction and study of the evolutionary relationships among individuals, populations or species to their ancestors. In the context of evolutionary biology, ancestral reconstruction can be used to recover different kinds of ancestral character states of organisms that lived millions of years ago. These states include the genetic sequence (ancestral sequence reconstruction), the amino acid sequence of a protein, the composition of a genome (e.g., gene order), a measurable characteristic of an organism ( phenotype), and the geographic range of an ancestral population or species (ancestral range reconstruction). This is desirable because it allows us to examine parts of phylogenetic trees corresponding to the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as regulatory sequences (see non-coding DNA), and often a substantial fraction of 'junk' DNA with no evident function. Almost all eukaryotes have mitochondria and a small mitochondrial genome. Algae and plants also contain chloroplasts with a chloroplast genome. The study of the genome is called genomics. The genomes of many organisms have been sequenced and various regions have been annotated. The International Human Genome Project reported the sequence of the genome for ''Homo sapiens'' in 200The Human Genome Project although the initial "finished" sequence was missing 8% of the genome consisting mostly of repetitive sequences. With advancements in technology that could handle sequen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lactose Intolerance
Lactose intolerance is a common condition caused by a decreased ability to digest lactose, a sugar found in dairy products. Those affected vary in the amount of lactose they can tolerate before symptoms develop. Symptoms may include abdominal pain, bloating, diarrhea, flatulence, and nausea. These symptoms typically start thirty minutes to two hours after eating or drinking milk-based food. Their severity typically depends on the amount a person eats or drinks. Lactose intolerance does not cause damage to the gastrointestinal tract. Lactose intolerance is due to the lack of the enzyme lactase in the small intestines to break lactose down into glucose and galactose. There are four types: primary, secondary, developmental, and congenital. Primary lactose intolerance occurs as the amount of lactase declines as people age. Secondary lactose intolerance is due to injury to the small intestine. Such injury could be the result of infection, celiac disease, inflammatory bowel disease ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Clock
The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleotide sequences for DNA, RNA, or amino acid sequences for proteins. The benchmarks for determining the mutation rate are often fossil or archaeological dates. The molecular clock was first tested in 1962 on the hemoglobin protein variants of various animals, and is commonly used in molecular evolution to estimate times of speciation or radiation. It is sometimes called a gene clock or an evolutionary clock. Early discovery and genetic equidistance The notion of the existence of a so-called "molecular clock" was first attributed to Émile Zuckerkandl and Linus Pauling who, in 1962, noticed that the number of amino acid differences in hemoglobin between different lineages changes roughly linearly with time, as estimated from fossil evi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient Pathogen Genomics
Ancient pathogen genomics is a scientific field related to the study of pathogen genomes recovered from ancient human, plant or animal remains. Ancient pathogens are microorganisms, now extinct, that in the past centuries caused several epidemics and deaths worldwide. Their genome, referred to as ancient DNA (aDNA), is isolated from the burial's remains (bones and teeth) of victims of the pandemics caused by these pathogens. The analysis of the genomic features of ancient pathogen genomes allows researchers to understand the evolution of modern microbial strains that can hypothetically generate new pandemics or outbreaks. The analysis of aDNA is carried out by bioinformatic tools and molecular biology techniques to compare ancient pathogens with the modern descendants. The comparison also provides phylogenetic information of these strains. Reconstructing ancient pathogen genomes through NGS technologies Pathogen DNA detection in ancient remains can be achieved with laboratory or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancestral Sequence Reconstruction
Ancestral sequence reconstruction (ASR) – also known as ancestral gene/sequence reconstruction/resurrection – is a technique used in the study of molecular evolution. The method uses related sequences to reconstruct an "ancestral" gene from a multiple sequence alignment. The method can be used to 'resurrect' ancestral proteins and was suggested in 1963 by Linus Pauling and Emile Zuckerkandl. In the case of enzymes, this approach has been called paleoenzymology (British: palaeoenzymology). Some early efforts were made in the 1980s and 1990s, led by the laboratory of Steven A. Benner, showing the potential of this technique. Thanks to the improvement of algorithms and of better sequencing and synthesis techniques, the method was developed further in the early 2000s to allow the resurrection of a greater variety of and much more ancient genes. Over the last decade, ancestral protein resurrection has developed as a strategy to reveal the mechanisms and dynamics of protein evolution ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Excavation (archaeology)
In archaeology, excavation is the exposure, processing and recording of archaeological remains. An excavation site or "dig" is the area being studied. These locations range from one to several areas at a time during a project and can be conducted over a few weeks to several years. Excavation involves the recovery of several types of data from a site. This data includes artifacts (portable objects made or modified by humans), features (non-portable modifications to the site itself such as post molds, burials, and hearths), ecofacts (evidence of human activity through organic remains such as animal bones, pollen, or charcoal), and archaeological context (relationships among the other types of data).Kelly&Thomas (2011). ''Archaeology: down to earth'' (4th ed.). Belmont, Calif.: Wadsworth, Cengage Learning. Before excavating, the presence or absence of archaeological remains can often be suggested by, non-intrusive remote sensing, such as ground-penetrating radar. Basic infor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slate (magazine)
''Slate'' is an online magazine that covers current affairs, politics, and culture in the United States. It was created in 1996 by former '' New Republic'' editor Michael Kinsley, initially under the ownership of Microsoft as part of MSN. In 2004, it was purchased by The Washington Post Company (later renamed the Graham Holdings Company), and since 2008 has been managed by The Slate Group, an online publishing entity created by Graham Holdings. ''Slate'' is based in New York City, with an additional office in Washington, D.C. ''Slate'', which is updated throughout the day, covers politics, arts and culture, sports, and news. According to its former editor-in-chief Julia Turner, the magazine is "not fundamentally a breaking news source", but rather aimed at helping readers to "analyze and understand and interpret the world" with witty and entertaining writing. As of mid-2015, it publishes about 1,500 stories per month. A French version, ''slate.fr'', was launched in February ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permafrost
Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface is underlain by permafrost, with the total area of around 18 million km2. This includes substantial areas of Alaska, Greenland, Canada and Siberia. It can also be located on mountaintops in the Southern Hemisphere and beneath ice-free areas in the Antarctic. Permafrost does not have to be the first layer that is on the ground. It can be from an inch to several miles deep under the Earth's surface. It frequently occurs in ground ice, but it can also be present in non-porous bedrock. Permafrost is formed from ice holding various types of soil, sand, and rock in combination. Permafrost contains large amounts of biomass and decomposed biomass that has been stored as methane and carbon dioxide, making tundra soil a carbon sink. As global wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
