Genes are working subunits of DNA. DNA is a vast chemical information database that carries the complete set of instructions for making all the proteins a cell will ever need. Each gene contains a particular set of instructions, usually coding for a particular protein.
DNA exists as two long, paired strands spiraled into the famous double helix. Each strand is made up of millions of chemical building blocks called bases. While there are only four different chemical bases in DNA (adenine, thymine, cytosine, and guanine), the order in which the bases occur determines the information available, much as specific letters of the alphabet combine to form words and sentences.
DNA resides in the core, or nucleus, of each of the body's trillions of cells. Every human cell (with the exception of mature red blood cells, which have no nucleus) contains the same DNA. Each cell has 46 molecules of double-stranded DNA. Each molecule is made up of 50 to 250 million bases housed in a chromosome.
The DNA in each chromosome constitutes many genes (as well as vast stretches of noncoding DNA, the function of which is unknown). A gene is any given segment along the DNA that encodes instructions that allow a cell to produce a specific product - typically, a protein such as an enzyme - that initiates one specific action. There are between 50,000 and 100,000 genes, and every gene is made up of thousands, even hundreds of thousands, of chemical bases.
Human cells contain two sets of chromosomes, one set inherited from the mother and one from the father. (Mature sperm and egg cells carry a single set of chromosomes.) Each set has 23 single chromosomes - 22 autosomes and an X or Y sex chromosome. (Females inherit an X from each parent, while males get an X from the mother and a Y from the father.)
For a cell to make protein, the information from a gene is copied, base by base, from DNA into new strands of messenger RNA (mRNA). Then mRNA travels out of the nucleus into the cytoplasm, to cell organelles called ribosomes. There, mRNA directs the assembly of amino acids that fold into completed protein molecule.
Each human cell contains 23 pairs of chromosomes, which can be distinguished by size and by unique banding patterns. This set is from a male, since it contains a Y chromosome. Females have two X chromosomes.
Different genes are activated in different cells, creating the specific proteins that give a particular cell type its character.
http://www.accessexcellence.org/AE/AEPC/NIH/gene03.php
All the functions of DNA depend on interactions with proteins. These protein interactions can be non-specific, or the protein can bind specifically to a single DNA sequence. Enzymes can also bind to DNA and of these, the polymerases that copy the DNA base sequence in transcription and DNA replication are particularly important.
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Structural proteins that bind DNA are well-understood examples of non-specific DNA-protein interactions. Within chromosomes, DNA is held in complexes with structural proteins. These proteins organize the DNA into a compact structure called chromatin. In eukaryotes this structure involves DNA binding to a complex of small basic proteins called histones, while in prokaryotes multiple types of proteins are involved.[64][65] The histones form a disk-shaped complex called a nucleosome, which contains two complete turns of double-stranded DNA wrapped around its surface. These non-specific interactions are formed through basic residues in the histones making ionic bonds to the acidic sugar-phosphate backbone of the DNA, and are therefore largely independent of the base sequence.[66] Chemical modifications of these basic amino acid residues include methylation, phosphorylation and acetylation.[67] These chemical changes alter the strength of the interaction between the DNA and the histones, making the DNA more or less accessible to transcription factors and changing the rate of transcription.[68] Other non-specific DNA-binding proteins found in chromatin include the high-mobility group proteins, which bind preferentially to bent or distorted DNA.[69] These proteins are important in bending arrays of nucleosomes and arranging them into more complex chromatin structures.[70]
A distinct group of DNA-binding proteins are the single-stranded-DNA-binding proteins that specifically bind single-stranded DNA. In humans, replication protein A is the best-characterised member of this family and is essential for most processes where the double helix is separated, including DNA replication, recombination and DNA repair.[71] These binding proteins seem to stabilize single-stranded DNA and protect it from forming stem-loops or being degraded by nucleases.
In contrast, other proteins have evolved to specifically bind particular DNA sequences. The most intensively studied of these are the various classes of transcription factors, which are proteins that regulate transcription. Each one of these proteins bind to one particular set of DNA sequences and thereby activates or inhibits the transcription of genes with these sequences close to their promoters. The transcription factors do this in two ways. Firstly, they can bind the RNA polymerase responsible for transcription, either directly or through other mediator proteins; this locates the polymerase at the promoter and allows it to begin transcription.[73] Alternatively, transcription factors can bind enzymes that modify the histones at the promoter; this will change the accessibility of the DNA template to the polymerase.[74]
As these DNA targets can occur throughout an organism's genome, changes in the activity of one type of transcription factor can affect thousands of genes.[75] Consequently, these proteins are often the targets of the signal transduction processes that mediate responses to environmental changes or cellular differentiation and development. The specificity of these transcription factors' interactions with DNA come from the proteins making multiple contacts to the edges of the DNA bases, allowing them to "read" the DNA sequence. Most of these base-interactions are made in the major groove, where the bases are most accessible.[76]
http://en.wikipedia.org/wiki/DNA
| Type of Camera | Compact digital camera |
| Effective Pixels | 10.0 million |
| Image Size (Pixels) | 3648 x 2736 (High: 3648 / Normal: 3648), 2592 x 1944 (Normal: 2592), 2048 x 1536 (Normal: 2048), 1024 x 768 (PC: 1024), 640 x 480 (TV: 640), 1920 x 1080 (16:9) |
| Lens | 5x Zoom-Nikkor; f/3.5-5.6 |
| Vibration Reduction | Electronic VR |
| Digital Zoom | Up to 4x |
| Focus Range | Normal mode: 35cm, Macro mode: 10 cm |
| LCD Monitor | 2.5"; 230,000-dot, wide viewing angle TFT LCD with anti-reflection coating |
| Storage Media | SD memory cards and internal memory (approx. 50MB) |
| File Format | Compressed JPEG, motion JPEG AVI, mono/wav file |
| Shooting Modes | Auto, Smile, Scene modes, High sensitivity, movie modes |
| Scene Modes | Portrait, Landscape, Sports, Night portrait, Party/indoor, Beach/snow, Sunset, Dusk/dawn, Night landscape, Close-up, Panorama assist, Museum, Fireworks show, Copy, Backlight |
| Capture Modes | Single, Continuous (approx. 1.3 fps), BSS (Best Shot Selector), Multi-shot 16 (16 frames in a single burst), Interval timer shooting |
| Video Recording | Yes (with sound) |
| Exposure Metering System | Matrix, Center-weighted, Spot |
| Sensitivity | Auto gain (ISO 64-800), High-sensitivity shooting mode (ISO 64-1600), Manual ISO 64, 100, 200, 400, 800, 1600, 2000 |
| White Balance | Auto, Preset manual, Daylight, Incandescent, Fluorescent, Cloudy, Flash |
| Self-Timer | 2 and 10 sec. duration |
| Flash Sync Modes | Auto, Auto with red-eye reduction, Off, Fill flash, Slow sync |
| Supported Languages | Total of 24 languages |
| Power Requirements | Rechargeable Li-ion Battery EN-EL11 (supplied), AC Adapter EH-62E (optional) |
| Battery Life (on a fully charged battery) | Approx. 200 shots with EN-EL11 battery (based on CIPA standard) |
| Dimensions | Approx. 90 x 53.5 x 22 mm excluding projections |
| Supplied Accessories (may differ by country or area) | Rechargeable Li-ion Battery EN-EL11, Battery Charger MH-64, AV/USB Cable UC-E12, Strap AN-CP14, Software Suite CD-ROM |
| Weight (without batteries and memory card) | Approx. 120 g |
