Ch. 13 - The Genetic Code and Transcription

Klug - Concepts of Genetics 12th Edition

Klug12th EditionConcepts of Genetics ISBN: 9780135564776당신이 사용하는 게 아니라요?교과서 변경

Klug 12th Edition

Ch. 13 - The Genetic Code and Transcription

문제 20

13장, 문제 20

Write a paragraph describing the abbreviated chemical reactions that summarize RNA polymerase-directed transcription.

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Begin by explaining that RNA polymerase-directed transcription is the process by which RNA polymerase synthesizes RNA from a DNA template strand.

Describe the initiation step where RNA polymerase binds to the promoter region of DNA, causing the DNA strands to unwind and expose the template strand.

Explain the elongation step, where RNA polymerase moves along the DNA template strand, adding ribonucleotides complementary to the DNA template, forming an RNA strand. This can be summarized by the reaction: \(\text{(DNA template)} + \text{rNTPs} \rightarrow \text{RNA} + \text{PPi}\), where rNTPs are ribonucleoside triphosphates and PPi is pyrophosphate.

Mention that the RNA strand grows in the 5' to 3' direction, with RNA polymerase catalyzing the formation of phosphodiester bonds between nucleotides.

Conclude with the termination step, where RNA polymerase reaches a termination signal on the DNA, causing the release of the newly synthesized RNA transcript and dissociation of RNA polymerase from the DNA.

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주요 개념

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RNA Polymerase Function

RNA polymerase is the enzyme responsible for synthesizing RNA from a DNA template during transcription. It binds to the promoter region, unwinds the DNA, and catalyzes the formation of phosphodiester bonds between ribonucleotides, creating a complementary RNA strand.

Transcription Process and Directionality

Transcription proceeds in the 5' to 3' direction, where RNA polymerase reads the DNA template strand in the 3' to 5' direction. Ribonucleoside triphosphates (NTPs) are added sequentially, releasing pyrophosphate and forming the growing RNA chain.

Chemical Reaction of Nucleotide Addition

The core chemical reaction involves the nucleophilic attack of the 3'-OH group of the growing RNA chain on the α-phosphate of an incoming NTP. This reaction forms a phosphodiester bond and releases pyrophosphate (PPi), which is subsequently hydrolyzed to drive the reaction forward.

관련 실천

교과서 질문

What observations suggested the existence of mRNA?

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교과서 질문

One form of posttranscriptional modification of most eukaryotic pre-mRNAs is the addition of a poly-A sequence at the 3' end. The absence of a poly-A sequence leads to rapid degradation of the transcript. Poly-A sequences of various lengths are also added to many bacterial RNA transcripts where, instead of promoting stability, they enhance degradation. In both cases, RNA secondary structures, stabilizing proteins, or degrading enzymes interact with poly-A sequences. Considering the activities of RNAs, what might be general functions of 3'-polyadenylation?

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교과서 질문

Define the process of transcription. Where does this process fit into the central dogma of molecular biology (DNA makes RNA makes protein)?

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교과서 질문

Present an overview of various forms of posttranscriptional RNA processing in eukaryotes. For each, provide an example.

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교과서 질문

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교과서 질문

Describe the structure of RNA polymerase in bacteria. What is the core enzyme? What is the role of the σ subunit?

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