New Developments in dsRNA

Recent research has also shown that a class of similar dsRNA fragments, called small temporal RNAs, play important roles in development in the roundworm, fruit fly, and other animals. Although little is so far known about them, these fragments are made by dicer from the cell's own RNA as gene expression use of a normal part of the developmental process and appear to help control gene a gene to create the expression. This is an exception to the statement that the presence of dsRNA signals a threat to the cell; how these are distinguished from threatening dsRNA is not yet known. see also Antisense Nucleotides; Fruit fly: Drosophila; Nucleases; RNA; Post-translational Control; RNA Processing; Roundworm: Caenorhabditis elegans; Transposable Genetic Elements; Virus.

Richard Robinson

Bibliography

Ambros, Victor. "Development: Dicing up RNAs." Science 293 (2001): 811-813.

Gura, Trisha. "A Silence that Speaks Volumes." Nature 404 (2000): 804-808.

Lin, Rueyling, and Leon Avery. "RNA Interference. Policing Rogue Genes." Nature 402 (1999): 128-129.

corresponding protein template a master copy synthesis creation

RNA Polymerases

RNA polymerases are enzyme complexes that synthesize RNA molecules using DNA as a template, in the process known as transcription. The RNAs created by transcription are either used as is (as ribosomal RNAs, transfer RNAs, or other types), or serve to guide the synthesis of a protein (as messenger RNAs). The word "polymerase" derives from "-ase," a suffix indicating an enzyme, and "polymer," meaning a large molecule composed of many similar parts, in this case the RNA nucleotides A, U, C, and G (abbreviations for adenine, uracil, cytosine, and guanine).

Transcribed DNA (upstream)

Growing RNA transcript

Growing RNA transcript

Entering DNA (downstream)

Incoming RNA nucleotides

Entering DNA (downstream)

Incoming RNA nucleotides

RNA polymerase use one side of the DNA double helix (blue) to assemble RNA nucleotides into an RNA transcript. The internal structure of the polymerase, shown in cutaway view, helps separate the DNA strands. A magnesium ion (Mg2+) helps catalyze the addition of RNA nucleotides into the growing chain. Adapted from <http://www .euchromatin.org/1844-1-med.gif>.

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