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DNA Transcription

Terms

Canonical promoter - Refers to the ideal configuration of a promoter region. The region includes three trademarks: the –35 region, the –10 region, and a 17 base pair space in between the two regions. The degree of conformity to this consensus sequence determines promoter strength. Only prokaryotes have canonical promoter regions.

Chromatin - The material of which chromosomes are made. Contains DNA, histones, and nonhistone proteins. Chromatin is found in the nucleus of eukaryotic cells.

Hairpin loop - A structure formed when a single strand of DNA or RNA folds back on itself via regions of complementary base pairing. Can be used as a termination signal for DNA transcription.

Hybrid - A complex that is a mixture of two distinct subunits.

Messenger RNA - An RNA molecule that specifies the amino acid sequence of a protein.

Nucleosome - A bead-like subunit of eukaryotic chromosomes. Composed of short lengths of DNA wrapped around histone proteins. A subunit of chromatin.

Promoter region - A specified region on a DNA chain that signals the initiation of DNA transcription.

Rho-dependent terminator - One class of stop signal for DNA transcription; dependent upon a protein called a "rho factor" that is thought to pull the RNA polymerase off the DNA template strand.

Rho-independent terminator - One class of stop signal for DNA transcription. Stretch of DNA that contains a sequence that is repeated in the reverse direction and is followed by a short string of adenines. When copied into RNA, it forms a hairpin loop that acts as a signal to stop transcription.

Ribonucleotide triphosphate - The building block for RNA synthesis. Contains a five-membered, oxygen- containing ring that has three phosphate groups attached to its 5' carbon and either an adenine, cytosine, guanine, or uracil base group attached to its 1' carbon.

Ribosomal RNA - An RNA molecule that forms a part of the structure of a ribosome and participates in protein synthesis.

RNA polymerase - The enzyme responsible for catalyzing the addition of ribonuclotide substrates to a growing RNA chain during DNA transcription.

Start site - A specific sequence on a DNA strand, located near a promoter region, which is recognized by RNA polymerase as the site for the addition of the first ribonucleotide substrate.

Transcription factor - Term applied to any protein required to initiate or regulate eukaryotic DNA transcription.

Transfer RNA - An RNA molecule used in protein synthesis as a link helping to convert messenger RNA into amino acids.

UP element - A promoter element characteristic of certain strong promoter regions. Consists of an AT rich region.

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