Acronym for asymmetric digital subscriber line. Technology and equipment allowing high-speed digital communication, including video signals, across an ordinary twisted-pair copper phone line, with speeds up to 8 Mbps (megabits per second) downstream (to the customer) and up to 640 Kbps (kilobits per second) upstream. ADSL access to the Internet is offered by some regional telephone companies, offering users faster connection times than those available through connections made over standard phone lines. Also called: asymmetric digital subscriber loop. Compare SDSL.
The data rate from the ISP is greater than the data rate to the ISP. For example, ADSL would deliver 6 million bits per second (6Mb/s) to the home, but only 384 thousand bits per second (384Kb/s) from the home to the ISP.
(Asymmetric Digital Subscriber Line)
Abbreviation of ribonucleic acid (which in the living cell transmits the genetic information coded in the DNA and acts as template for protein synthesis).
(abbreviation for ribonucleic acid) Nucleic acid involved in the process of translating DNA, the genetic material into proteins. It is usually single-stranded, unlike the double-stranded DNA, and consists of a large number of nucleotides strung together, each of which comprises the sugar ribose, a phosphate group, and one of four bases (uracil, cytosine, adenine, or guanine).
RNA is copied from DNA by the assemblage of free nucleotides against an unwound portion (a single strand) of the DNA, with DNA serving as the template. In this process, uracil (instead of the thymine in DNA) is paired with adenine, and guanine with cytosine, forming base pairs that then separate. The RNA then travels to the ribosomes where it serves to assemble proteins from free amino acids. In a few viruses, such as retroviruses, RNA is the only hereditary material.
RNA occurs in three major forms, each with a different function in the synthesis of protein molecules. Messenger RNA (mRNA) acts as the template for protein synthesis. Each codon (a set of three bases) on the RNA molecule is matched up with the corresponding amino acid, in accordance with the genetic code. This process (translation) takes place in the ribosomes, which are made up of proteins and ribosomal RNA (rRNA). Transfer RNA (tRNA) is responsible for combining with specific amino acids, and then matching up a special “anticodon” sequence of its own with a codon on the mRNA.
This is how the genetic code is translated into proteins.