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Transcription - mRNA transcript Processing the mRNA...

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Transcription Transcription is the synthesis of mRNA from a DNA template. It is like DNA replication in that a DNA strand is used to synthesize a strand of mRNA. Only one strand of DNA is copied. A single gene may be transcribed thousands of times. After transcription, the DNA strands rejoin. Steps involved in transcription RNA polymerase recognizes a specific base sequence in the DNA called a promoter and binds to it. The promoter identifies the start of a gene, which strand is to be copied, and the direction that it is to be copied. RNA polymerase unwinds the DNA. RNA polymerase assembles bases that are complimentary to the DNA strand being copied. RNA contains uracil instead of thymine. A termination code in the DNA indicates where transcription will stop. The mRNA produced is called a
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Unformatted text preview: mRNA transcript . Processing the mRNA Transcript In eukaryotic cells, the newly-formed mRNA transcript (also called heterogenous nuclear RNA or hnRNA) must be further modified before it can be used. A cap is added to the 5’ end and a poly-A tail (150 to 200 Adenines) is added to the 3’end of the molecule. Eukaryotic genes contain regions that are not translated into proteins. These regions of DNA are called introns and must be removed from mRNA. Their function is not well understood. The remaining portions of DNA that are translated into protein are called exons . After intron-derived regions are removed from mRNA, the remaining fragments- derived from exons- are spliced together to form a mature mRNA transcript ....
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