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Which Region Of The Dna Strands Shown Could Serve As A Template

Written By Thursday, April 14, 2022 Add Comment Edit

A schematic shows two horizontal strands of DNA against a white background, one in the lower half of the image and one arcing in the upper half. A transparent green globular structure, representing the enzyme RNA polymerase, is bound to a several-nucleotide-long region along the lower DNA strand about 60% of the way from the left side. The sugar-phosphate backbone of the DNA strand is depicted as a segmented grey cylinder, whereas the sugar-phosphate backbone of the RNA strand is depicted as a segmented white cylinder. DNA nitrogenous bases are represented as blue, orange, red, or green vertical rectangles attached to each segment of the sugar-phosphate backbone; RNA nitrogenous bases are represented by blue, green, orange, and yellow vertical rectangles attached to each segment of the sugar-phosphate backbone. RNA polymerase synthesizes a complementary RNA strand, forming DNA-RNA pairs of orange-blue, red-green, blue-orange, or green-yellow, consistent with a thymine to uracil substitution in the RNA strand. About three dozen individual nucleotides float in the background. One individual nucleotide is visible inside the transparent enzyme at a higher magnification.

Figure 2: RNA polymerase (green) synthesizes a strand of RNA that is complementary to the Dna template strand below it.

Once RNA polymerase and its related transcription factors are in place, the unmarried-stranded DNA is exposed and set for transcription. At this betoken, RNA polymerase begins moving down the Dna template strand in the three' to 5' management, and as it does then, information technology strings together complementary nucleotides. Past virtue of complementary base- pairing, this action creates a new strand of mRNA that is organized in the v' to 3' direction. As the RNA polymerase continues down the strand of Dna, more than nucleotides are added to the mRNA, thereby forming a progressively longer chain of nucleotides (Effigy 2). This process is called elongation.

A schematic compares a single-stranded DNA molecule with a single-stranded RNA molecule with a similar sequence. Both RNA and DNA contain nitrogenous bases, represented by vertical colored rectangles, attached to a sugar-phosphate backbone, represented as a segmented cylinder. There are two major differences between the composition of RNA and DNA strands. The sugar in the DNA strand is deoxyribose, represented by a grey cylinder, whereas the sugar in the RNA strand is ribose, represented by a white cylinder. In addition, the nitrogenous base thymine (red) in the DNA strand is replaced by uracil (yellow) in the RNA strand.

Figure iii: Deoxyribonucleic acid (acme) includes thymine (scarlet); in RNA (bottom), thymine is replaced with uracil (yellow).

Three of the four nitrogenous bases that brand up RNA — adenine (A), cytosine (C), and guanine (G) — are also found in Dna. In RNA, however, a base called uracil (U) replaces thymine (T) as the complementary nucleotide to adenine (Figure 3). This means that during elongation, the presence of adenine in the Deoxyribonucleic acid template strand tells RNA polymerase to adhere a uracil in the corresponding surface area of the growing RNA strand (Figure iv).

A schematic shows two rows of nucleotides. Each individual nucleotide is represented as an elongated, vertical, colored rectangle (a nitrogenous base) bound at one end to a grey horizontal cylinder (a sugar molecule). The top row of nucleotides is from RNA, with an A-C-U-G base sequence. The bottom row of nucleotides is from DNA, with a T-G-A-C base sequence.

Figure iv: A sample section of RNA bases (upper row) paired with DNA bases (lower row). When this base of operations-pairing happens, RNA uses uracil (xanthous) instead of thymine to pair with adenine (green) in the Deoxyribonucleic acid template below.

Interestingly, this base of operations substitution is not the simply difference betwixt DNA and RNA. A 2d major departure between the ii substances is that RNA is made in a single-stranded, nonhelical form. (Call back, Dna is almost always in a double-stranded helical form.) Furthermore, RNA contains ribose sugar molecules, which are slightly different than the deoxyribosemolecules institute in Deoxyribonucleic acid. As its name suggests, ribose has more than oxygen atoms than deoxyribose.

Thus, the elongation period of transcription creates a new mRNA molecule from a unmarried template strand of DNA. As the mRNA elongates, information technology peels away from the template as information technology grows (Figure 5). This mRNA molecule carries DNA'southward message from the nucleus to ribosomes in the cytoplasm, where proteins are assembled. However, before it can do this, the mRNA strand must split itself from the Dna template and, in some cases, it must also undergo an editing process of sort.

A schematic shows two strands of DNA against a white background, each going from the lower left to the upper middle of the frame. A transparent green globular structure, representing the enzyme RNA polymerase, is bound to a several-nucleotide-long region along the lower DNA strand. The sugar-phosphate backbone of the DNA is depicted as a segmented grey cylinder. Nitrogenous bases are represented as colored vertical rectangles attached to each segment on the sugar-phosphate backbone. A newly synthesized RNA strand is shown in the foreground of the illustration. It snakes down to the RNA polymerase. In the RNA strand, uracil, represented by a yellow base, has been inserted in place of thymine.

Figure 5: During elongation, the new RNA strand becomes longer and longer as the DNA template is transcribed. In this view, the v' end of the RNA strand is in the foreground. Notation the inclusion of uracil (yellow) in RNA.

Which Region Of The Dna Strands Shown Could Serve As A Template,

Source: http://www.nature.com/scitable/topicpage/the-information-in-dna-is-decoded-by-6524808

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