Summary of transcription and translation for exam 4

Summary of transcription and translation for exam 4 -...

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Review of Transcription and Translation for Exam 4 Transcription (Bacteria)- Initiation- 1. The holopolymerase binds to the promoter, which consists of the consensus sequences TTGACAT at -35 and TATAAT at -10 using the sigma factor. The holopolymerase is held to these consensus sequences by the hydrogen bonding that occurs between the holopolymerase and the edges of the bases within the groove. 2. Binding energy is used to unwind and unpair the DNA about 20 base pairs around the +1 start site to form the open complex. 3. Transcription begins 4-7 base pairs downstream of the -10 consensus sequence. 4. The open complex is used as a template; NTPs diffuse in and begin forming phosphoester bonds and releasing Ppi. 3-9 phosphoester bonds are formed in this manner. This is called the initation complex. 5. The initation complex undergoes a transition where the sigma factor is lost. The core polymerase is now able to move down the DNA, synthesizing the nascant RNA is a 5’ to 3’ direction. Elongation- 1. Following initiation, the elongation complex remains. The core polymerase, composed of alpha, beta, beta prime, and omega subunits, moves down the polymerse molecule unwinding and unpairing the DNA as it goes. It maintains a bubble of approximately 15 nucleotides as it goes. 2. This continues until the polymerase reaches an inverted repeat followed by a string of A’s on the template strand. Termination- 1. After polymerase reaches an inverted repeat and transcribes it, the inverted repeat forms a hairpin loop of intrastrand base pairing. 2. Polymerase then reaches the string of A’s on the template strand and tries to incorporate U’s but is only able to incorporate a few. 3. The polymerase molecule falls off and the RNA is released. Transcription (Eukaryotes)-
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Summary of transcription and translation for exam 4 -...

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