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Вы можете ознакомиться и скачать презентацию на тему Транскрипция. Доклад-сообщение содержит 15 слайдов. Презентации для любого класса можно скачать бесплатно. Если материал и наш сайт презентаций Mypresentation Вам понравились – поделитесь им с друзьями с помощью социальных кнопок и добавьте в закладки в своем браузере.

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Транскрипция Key Terms The coding strand (Sense strand) of DNA has the same sequence as the mRNA and is related by the genetic code to the protein sequence that it represents. The antisense strand (Template strand) of DNA is complementary to the sense strand, and is the one that acts as the template for synthesis of mRNA. RNA polymerases are enzymes that synthesize RNA using a DNA template (formally described as DNA-dependent RNA polymerases). A promoter is a region of DNA where RNA polymerase binds to initiate transcription. Startpoint (startsite) (Startsite) refers to the position on DNA corresponding to the first base incorporated into RNA. A terminator is a sequence of DNA that causes RNA polymerase to terminate transcription. A transcription unit is the distance between sites of initiation and termination by RNA polymerase; may include more than one gene. Upstream identifies sequences proceeding in the opposite direction from expression; for example, the bacterial promoter is upstream of the transcription unit, the initiation codon is upstream of the coding region. Downstream identifies sequences proceeding farther in the direction of expression; for example, the coding region is downstream of the initiation codon. A primary transcript is the original unmodified RNA product corresponding to a transcription unit.

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Transcription occurs by base pairing in a bubble" of unpaired DNA ·RNA polymerase separates the two strands of DNA in a transient "bubble" and uses one strand as a template to direct synthesis of a complementary sequence of RNA.The length of the bubble is ~12-14 bp, and the length of RNA-DNA hybrid within it ~8-9 bp.

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Initiation describes the stages of transcription up to synthesis of the first bond in RNA. This includes binding of RNA polymerase to the promoter and melting a short region of DNA into single strands. Initiation describes the stages of transcription up to synthesis of the first bond in RNA. This includes binding of RNA polymerase to the promoter and melting a short region of DNA into single strands. Elongation is the stage in a macromolecular synthesis reaction (replication, transcription, or translation) when the nucleotide or polypeptide chain is being extended by the addition of individual subunits. During elongation the transcription bubble moves along DNA and the RNA chain is extended in the 5’ – 3’ direction. Termination is a separate reaction that ends a macromolecular synthesis reaction (replication, transcription, or translation), by stopping the addition of subunits, and (typically) causing disassembly of the synthetic apparatus. Transcription stops, the DNA duplex reforms and RNA polymerase dissociates at a terminator site.

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T7 RNA polymerase has a specificity loop that binds positions -7 to -11 of the promoter while positions -1 to -4 enter the active site.

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DNA moves through a groove in yeast RNA polymerase that makes a sharp turn at the active site. A protein bridge changes conformation to control the entry of nucleotides to the active site.

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Ten subunits of RNA polymerase are placed in position from the crystal structure. The colors of the subunits are the same as in the crystal structures of the following figures.