The first two questions face anyone who cares to distinguish the real from the unreal and the true from the false. The third question faces anyone who makes any decisions at all, and even not deciding is itself a decision. Thus all persons practice philosophy whether they know it or not. Autocosmic Answers What is existing?
Since the s the accumulation of spontaneous mutations in the DNA of organs and tissues has been hypothesized to underlie aging itself e. What are mutations, and why are they there? DNA damage consists of chemical alterations in DNA structure, leading to a structure that can no longer serve as a substrate for faithful replication or transcription.
DNA damage cannot be copied to end up in daughter cells. DNA mutations are heritable changes in a DNA sequence of an organism, which can be part of a gene, a gene regulatory region, or some noncoding part of the genome. Mutations are usually introduced as a consequence of misreplication or misrepair, for example, due to the presence of DNA damage.
Hence, DNA damage can lead to mutations when it is not correctly repaired. Mutations can vary from point mutations, involving single or very few base pairs to large deletions, insertions, duplications, and inversions.
In organisms with multiple chromosomes, DNA from one chromosome can be joined to another and the actual chromosome number can be affected. Indeed, they fuel the survival of cells and organisms in times of stress.
They are the substrate for evolution, which gave rise to different life forms.
In both prokaryotic and eukaryotic cells mutation rate can be greatly increased, causing many cells to die but also giving rise to cells with the necessary attributes to survive and expand. Cancer cells, for example, can undergo mutations in genes that control the mutation rate for example, genes involved in DNA repair.
Such "mutator phenotypes" allow them to accelerate the acquisition of novel attributes e. While in such cases mutations are detrimental for the host, they are beneficial for the cell.
In most cases, mutations will have adverse effects on both the host and the cell. In the somatic cells of multicellular organisms, however, mutations usually have adverse effects.
Gross chromosomal alterations The earliest and still the most popular way to look at mutations is by cytogenetic means.
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This necessarily precludes the detection of mutational events smaller than a few million base pairs and also limits the target tissue to cells in metaphase, usually white blood cells. A noteworthy exception to this latter limitation is the original work of the late Howard Curtiswho with coworkers examined mouse liver parenchymal cell metaphase plates after partial hepatectomy and found considerably higher numbers of cells with abnormal chromosomes in old, compared with young, animals i.
Later, large structural changes in DNA were observed to increase with donor age in white blood cells of human individuals, from about 2—4 percent of the cells having chromosomal aberrations in young individuals to about six times higher in the elderly.
The recent use of more advanced methods, such as chromosome painting, have confirmed the increase in cytogenetic damage with age in both human and mouse. In both human and mouse lymphocytes the increase in chromosome aberrations appeared to be exponential. Mutations detected in selectable marker genes With the development of tests based on selectable endogenous marker genes, it became possible to assess mutation frequencies at these loci in T-cells from human and animal donors for a review see Vijg, Using the hypoxanthine phosphoribosyl transferase HPRT locus test, investigators have shown that mutation frequencies at this locus increase with donor age.
In mice mutation frequencies have been reported from about 5 x in young animals to about 3 x in middle aged mice Dempsey et al. However, in both mice and humans these values could be underestimates, due to the loss of HPRT mutants in vivo or in vitro.Dear Twitpic Community - thank you for all the wonderful photos you have taken over the years.
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An automatic spot identification method is developed for high throughput surface plasmon resonance imaging (SPRi) analysis. As a combination of video accessing, image enhancement, image processing and parallel processing techniques, the method can identify the spots in SPRi images of the microarray from SPRi video data.
In some circles, however, opposition to the concept of evolution has persisted to the present. The argument from design has recently been revived by a number of academics with scientific credentials, who maintain that their version of the idea (unlike Paley’s) is soundly supported by both microbiology and mathematics.
MDPI is a publisher of peer-reviewed, open access journals since its establishment in Techniques for Cell Preservation Many industries such as the food, pharmaceutical and horticultural industries require an extensive use of various types of cells.
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