Protein Synthesis - Transcription
Transcription is the process through which DNA is copied into mRNA. The first step of protein synthesis, this is how the instructions on how to build a protein are transferred from DNA to ribosomes. Transcription takes place in four steps:
1. RNA Polymerase binds to the promoter region of DNA - a portion of the DNA that signals the beginning of a Transcription Unit (unit of DNA to be copied). 2. RNA Polymerase opens up the double helix and begins to transcribe DNA on one side only. RNA nucleotides match up with the corresponding DNA nucleotides and RNA polymerase binds the RNA nucleotides together, with one difference. Instead of binding T-A, Thymine is replaced with Uracil. 3. RNA polymerase opens up more of the helix and continues transcribing the DNA until it reaches a termination sequence. Termination sequences are a specific combination of three nucleotides, that together form a stop codon, signaling the end of transcription. The RNA begins to float away and the already copied DNA coils back up. 4. The RNA drifts off into the nucleus for splicing, DNA coils fully back up, and RNA Polymerase moves off to transcribe other DNA strands. The RNA formed is called mRNA (messenger RNA) and is used to transport information on how to build proteins. |
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Transcription occurs within the nucleus. |
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Transcription Pictures: page 332 of Campbell Biology Ninth Edition
Transcription Video: http://www.youtube.com/watch?v=SMtWvDbfHLo&list=PLD0D5F297744AD515&index=16&feature=plpp_video
Roisen Review Video: http://www.youtube.com/watch?v=M5LKPadiWdU&feature=autoplay&list=PL9CAF3DEF0A718A50&index=52&playnext=1
Transcription Video: http://www.youtube.com/watch?v=SMtWvDbfHLo&list=PLD0D5F297744AD515&index=16&feature=plpp_video
Roisen Review Video: http://www.youtube.com/watch?v=M5LKPadiWdU&feature=autoplay&list=PL9CAF3DEF0A718A50&index=52&playnext=1