Archival processing is a well-established method for organizing collections this way.
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However, the current archival workflow leads to artificial boundaries between materials and delays in getting digitized content online because physical and born-digital materials are processed independently, and digitized materials not at all. In response, this work explores the approach of processing materials in a digitized form using a large multi-touch table.
This alternative workflow provides the first step towards integrating the archival processing of digital and physical materials, and can expedite the process of making the materials available online. However, this approach demands high quality digitization and requires that archivists perform additional tasks like matching multi-sided, multi-paged documents. A unique arrangement : Organizing collections for digital libraries, archives, and repositories.
- Fallen From Grace.
- Burnt Creek.
- A unique arrangement: Organizing collections for digital libraries, archives, and repositories.
N2 - Digital libraries increasingly host collections that are archival in nature, and contain digitized and born-digital materials. AB - Digital libraries increasingly host collections that are archival in nature, and contain digitized and born-digital materials. Abstract Digital libraries increasingly host collections that are archival in nature, and contain digitized and born-digital materials.
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Digital Libraries. Beyond the ladder-like structure described above, another key characteristic of double-stranded DNA is its unique three-dimensional shape. The first photographic evidence of this shape was obtained in , when scientist Rosalind Franklin used a process called X-ray diffraction to capture images of DNA molecules Figure 5. Although the black lines in these photos look relatively sparse, Dr.
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Franklin interpreted them as representing distances between the nucleotides that were arranged in a spiral shape called a helix. Around the same time, researchers James Watson and Francis Crick were pursuing a definitive model for the stable structure of DNA inside cell nuclei. Watson and Crick ultimately used Franklin's images, along with their own evidence for the double-stranded nature of DNA, to argue that DNA actually takes the form of a double helix , a ladder-like structure that is twisted along its entire length Figure 6.
Franklin, Watson, and Crick all published articles describing their related findings in the same issue of Nature in Most cells are incredibly small. For instance, one human alone consists of approximately trillion cells. Yet, if all of the DNA within just one of these cells were arranged into a single straight piece, that DNA would be nearly two meters long!
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So, how can this much DNA be made to fit within a cell? The answer to this question lies in the process known as DNA packaging , which is the phenomenon of fitting DNA into dense compact forms Figure 7.
During DNA packaging, long pieces of double-stranded DNA are tightly looped, coiled, and folded so that they fit easily within the cell. Eukaryotes accomplish this feat by wrapping their DNA around special proteins called histones , thereby compacting it enough to fit inside the nucleus Figure 8. Together, eukaryotic DNA and the histone proteins that hold it together in a coiled form is called chromatin. It is impossible for researchers to see double-stranded DNA with the naked eye — unless, that is, they have a large amount of it. Modern laboratory techniques allow scientists to extract DNA from tissue samples, thereby pooling together miniscule amounts of DNA from thousands of individual cells.
When this DNA is collected and purified, the result is a whitish, sticky substance that is somewhat translucent. To actually visualize the double-helical structure of DNA, researchers require special imaging technology, such as the X-ray diffraction used by Rosalind Franklin. However, it is possible to see chromosomes with a standard light microscope, as long as the chromosomes are in their most condensed form.
To see chromosomes in this way, scientists must first use a chemical process that attaches the chromosomes to a glass slide and stains or "paints" them. Staining makes the chromosomes easier to see under the microscope. In addition, the banding patterns that appear on individual chromosomes as a result of the staining process are unique to each pair of chromosomes, so they allow researchers to distinguish different chromosomes from one another.
Then, after a scientist has visualized all of the chromosomes within a cell and captured images of them, he or she can arrange these images to make a composite picture called a karyotype Figure This page appears in the following eBook.
Aa Aa Aa. What components make up DNA? Opposite to the 5' side of the sugar molecule is the 3' side dark gray , which has a free hydroxyl group attached not shown. Although nucleotides derive their names from the nitrogenous bases they contain, they owe much of their structure and bonding capabilities to their deoxyribose molecule.
The central portion of this molecule contains five carbon atoms arranged in the shape of a ring, and each carbon in the ring is referred to by a number followed by the prime symbol '. Of these carbons, the 5' carbon atom is particularly notable, because it is the site at which the phosphate group is attached to the nucleotide.
Appropriately, the area surrounding this carbon atom is known as the 5' end of the nucleotide. Opposite the 5' carbon, on the other side of the deoxyribose ring, is the 3' carbon, which is not attached to a phosphate group. This portion of the nucleotide is typically referred to as the 3' end Figure 1. When nucleotides join together in a series, they form a structure known as a polynucleotide. At each point of juncture within a polynucleotide, the 5' end of one nucleotide attaches to the 3' end of the adjacent nucleotide through a connection called a phosphodiester bond Figure 3.
It is this alternating sugar-phosphate arrangement that forms the "backbone" of a DNA molecule. This backbone is formed when the 3' end dark gray of one nucleotide attaches to the 5' phosphate end light gray of an adjacent nucleotide by way of a phosphodiester bond. How is the DNA strand organized? Within this arrangement, each strand mirrors the other as a result of the anti-parallel orientation of the sugar-phosphate backbones, as well as the complementary nature of the A-T and C-G base pairing. Figure Detail. How is DNA packaged inside cells? What does real chromatin look like?
A Unique Arrangement: Organizing Collections for Digital Libraries, Archives, and Repositories
Compare the relative sizes of the double helix, histones, and chromosomes. How do scientists visualize DNA? Watch this video for a closer look at the relationship between chromosomes and the DNA double helix. What are karyotypes used for?