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Paleovirology
Paleovirology is the study of viruses that existed in the past but are now extinct. In general, viruses cannot leave behind physical fossils, therefore indirect evidence is used to reconstruct the past. For example, viruses can cause evolution of their hosts, and the signatures of that evolution can be found and interpreted in the present day. Also, some viral genetic fragments which were integrated into germline cells of an ancient organism have been passed down to our time as viral fossils, or endogenous viral elements (EVEs). EVEs that originate from the integration of retroviruses are known as endogenous retroviruses, or ERVs, and most viral fossils are ERVs. They may preserve genetic code from millions of years ago, hence the "fossil" terminology, although no one has detected a virus in mineral fossils. The most surprising viral fossils originate from non-retroviral DNA virus, DNA and RNA viruses. Terminology Although there is no formal classification system for EVEs, they are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endogenous Viral Element
An endogenous viral element (EVE) is a DNA sequence derived from a virus, and present within the germline of a non-viral organism. EVEs may be entire viral genomes ( proviruses), or fragments of viral genomes. They arise when a viral DNA sequence becomes integrated into the genome of a germ cell that goes on to produce a viable organism. The newly established EVE can be inherited from one generation to the next as an allele in the host species, and may even reach fixation. Endogenous retroviruses and other EVEs that occur as proviruses can potentially remain capable of producing infectious virus in their endogenous state. Replication of such 'active' endogenous viruses can lead to the proliferation of viral insertions in the germline. For most non-retroviral viruses, germline integration appears to be a rare, anomalous event, and the resulting EVEs are often only fragments of the parent virus genome. Such fragments are usually not capable of producing infectious virus, but may e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endogenous Retroviruses
Endogenous retroviruses (ERVs) are endogenous viral elements in the genome that closely resemble and can be derived from retroviruses. They are abundant in the genomes of jawed vertebrates, and they comprise up to 5–8% of the human genome (lower estimates of ~1%). ERVs are a vertically inherited proviral sequence and a subclass of a type of gene called a transposon, which can normally be packaged and moved within the genome to serve a vital role in gene expression and in regulation. ERVs however lack most transposon functions, are typically not infectious and are often defective genomic remnants of the retroviral replication cycle. They are distinguished as germline provirus retroelements due to their integration and reverse-transcription into the nuclear genome of the host cell. Researchers have suggested that retroviruses evolved from a type of transposon called a retrotransposon, a Class I element; these genes can mutate and instead of moving to another location in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Ev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleobiology
Paleobiology (or palaeobiology) is an interdisciplinary field that combines the methods and findings found in both the earth sciences and the life sciences. Paleobiology is not to be confused with geobiology, which focuses more on the interactions between the biosphere and the physical Earth. Paleobiological research uses biological field research of current biota and of fossils millions of years old to answer questions about the molecular evolution and the evolutionary history of life. In this scientific quest, macrofossils, microfossils and trace fossils are typically analyzed. However, the 21st-century biochemical analysis of DNA and RNA samples offers much promise, as does the biometric construction of phylogenetic trees. An investigator in this field is known as a paleobiologist. Important research areas *Paleobotany applies the principles and methods of paleobiology to flora, especially green land plants, but also including the fungi and seaweeds (algae). See also myc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micropaleontology
Micropaleontology (American spelling; spelled micropalaeontology in European usage) is the branch of paleontology (palaeontology) that studies microfossils, or fossils that require the use of a microscope to see the organism, its morphology and its characteristic details. Microfossils Microfossils are fossils that are generally between 0.001mm and 1 mm in size, the study of which requires the use of light or electron microscopy. Fossils which can be studied by the naked eye or low-powered magnification, such as a hand lens, are referred to as macrofossils. For example, some colonial organisms, such as Bryozoa (especially the Cheilostomata) have relatively large colonies, but are classified by fine skeletal details of the small individuals of the colony. In another example, many fossil genera of Foraminifera, which are protists are known from shells (called "tests") that were as big as coins, such as the genus '' Nummulites''. Microfossils are a common feature of the g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Invertebrate Iridescent Virus 31
''Invertebrate iridescent virus 31'' (IIV-31), also known informally as isopod iridovirus, is a species of invertebrate iridescent virus in the genus ''Iridovirus''. Oniscidea (commonly known by a variety of names including ''woodlouse'', ''pillbug'', ''slater'', ''rolly-polly'', ''potato bug'', et al.) serve as hosts. Infection is associated with decreased responsiveness in the host, increased mortality, and most strikingly, the emergence of an iridescent blue or bluish-purple colour due to the reflection of light off a paracrystalline arrangement of virions within the tissues. Taxonomy In earlier centuries, blue individuals of otherwise drab oniscidean species had been discovered. They were sometimes interpreted to be new subspecies and were described as such: ''Ligidium hypnorum coeruleum'' Lereboullet 1843 and ''L. hypnorum amethystinum'' Schöbl 1861 (in reference to cerulean and amethyst, respectively). In 1980, the first research was published showing that the phenomeno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endogenous Viral Element
An endogenous viral element (EVE) is a DNA sequence derived from a virus, and present within the germline of a non-viral organism. EVEs may be entire viral genomes ( proviruses), or fragments of viral genomes. They arise when a viral DNA sequence becomes integrated into the genome of a germ cell that goes on to produce a viable organism. The newly established EVE can be inherited from one generation to the next as an allele in the host species, and may even reach fixation. Endogenous retroviruses and other EVEs that occur as proviruses can potentially remain capable of producing infectious virus in their endogenous state. Replication of such 'active' endogenous viruses can lead to the proliferation of viral insertions in the germline. For most non-retroviral viruses, germline integration appears to be a rare, anomalous event, and the resulting EVEs are often only fragments of the parent virus genome. Such fragments are usually not capable of producing infectious virus, but may e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endogenous Retrovirus
Endogenous retroviruses (ERVs) are endogenous viral elements in the genome that closely resemble and can be derived from retroviruses. They are abundant in the genomes of jawed vertebrates, and they comprise up to 5–8% of the human genome (lower estimates of ~1%). ERVs are a vertically inherited proviral sequence and a subclass of a type of gene called a transposon, which can normally be packaged and moved within the genome to serve a vital role in gene expression and in regulation. ERVs however lack most transposon functions, are typically not infectious and are often defective genomic remnants of the retroviral replication cycle. They are distinguished as germline provirus retroelements due to their integration and reverse-transcription into the nuclear genome of the host cell. Researchers have suggested that retroviruses evolved from a type of transposon called a retrotransposon, a Class I element; these genes can mutate and instead of moving to another location in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PLOS Biology
''PLOS Biology'' is a monthly peer-reviewed scientific journal covering all aspects of biology. Publication began on October 13, 2003. It is the first journal published by the Public Library of Science. The editor-in-chief is Nonia Pariente. In addition to research articles, the journal publishes magazine content aimed to be accessible to a broad audience. Article types in this section are essays, "unsolved mysteries", editorials, and synopses. Abstracting and indexing The journal is abstracted and indexed in: *Biological Abstracts *BIOSIS Previews *''Current Contents''/Agriculture, Biology & Environmental Sciences *''Current Contents''/Life Sciences *Chemical Abstracts Service * Embase *''Index Medicus''/MEDLINE/PubMed *Science Citation Index *Scopus *''The Zoological Record'' According to ''Journal Citation Reports'', the journal had a 2019 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a scientometric index calculated by Clariv ... [...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 war ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insertional Mutagenesis
In molecular biology, insertional mutagenesis is the creation of mutations of DNA by addition of one or more base pairs. Such insertional mutations can occur naturally, mediated by viruses or transposons, or can be artificially created for research purposes in the lab. Signature tagged mutagenesis This is a technique used to study the function of genes. A transposon such as the P element of ''Drosophila melanogaster'' is allowed to integrate at random locations in the genome of the organism being studied. Mutants generated by this method are then screened for any unusual phenotypes. If such a phenotype is found then it can be assumed that the insertion has caused the gene relating to the usual phenotype to be inactivated. Because the sequence of the transposon is known, the gene can be identified, either by sequencing the whole genome and searching for the sequence, or using the polymerase chain reaction to amplify specifically that gene. Virus insertional mutagenesis Beca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
