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Molecular Information Flow and Protein Processing - Transcription in Bacteria

Q: Five subunits of RNA polymerase and form the RNAP core enzyme responsible for RNA synthesis using DNA as template and ribonucleotide (rNTP) as substrate.

α (two copies), β, β', σ and ω subunits.

14 important questions on Molecular Information Flow and Protein Processing - Transcription in Bacteria

What enzyme catalyzes transcription and forms phosphodiester bonds between the ribonucleotides?

RNA polymerase

Driven by energy released from the hydrolysis of two energy-rich phosphate bonds of the incoming ribonucleoside triphosphates.

Polymerization

How is the mechanism of RNA synthesis similar to that of DNA synthesis?

During elongation of an RNA chain, ribonucleoside triphosphates are added to the 3′-OH of the ribose of the preceding nucleotide. Thus chain growth is 5′--> 3′ just as in DNA synthesis, and the newly
synthesized strand of RNA runs antiparallel to the DNA template strand it was transcribed from.

Transcription continues until specific sequences called _ ___are reached, but unlike DNA replication, which copies the entire
genome, transcription occurs on much smaller units of DNA, often
as little as a single gene.

transcription terminators

Five subunits of RNA polymerase and form the RNAP core enzyme responsible for RNA synthesis using DNA as template and ribonucleotide (rNTP) as substrate.

α (two copies), β, β', σ and ω subunits.

The core enzyme alone synthesizes RNA, and sigma functions only to recognize the appropriate site on the DNA for transcription to begin (sigma dissociates from the holoenzyme once

a short sequence of RNA has been formed). Once sigma dissociates, _____ is formed.

RNA polymerase core enzyme, α2ββ′ω.

Why does transcription occur in opposite directions on the two different strands of DNA?

Because some genes reside
on one strand of DNA while other genes reside on the other strand of
DNA, promoters (initiation sites) are present on both strands.

2 highly conserved regions in the promoter that are upstream of (prior to) the transcription start site

10 bases upstream, the -10 region, or Pribnow box.
- TATAAT
35 bases upstream of the start site
-TTGACA

Promoters that conform most closely to the consensus sequence and are effective in binding RNA polymerase.

Strong promoters

Why is the presence or absence of a specific sigma factor is a mechanism for
regulating gene expression?

Each alternative sigma factor is specific for a group of genes required under special circumstances. By changing the rate of either synthesis or degradation of a particular sigma factor, the cell can control the transcription of entire gene families.

Segments of DNA that are transcribed into a single RNA molecule bounded by their initiation and termination sites

Transcriptional units

Three size classes of prokaryotic rRNA:

16S, 23S and 5S

S = Svedberg unit

RNA polymerase proceeds through the operon and transcribes the entire set of genes into a single mRNA called _____. It contains multiple open reading frames.

Polycistronic mRNA

Portions of the mRNA that actually encode amino acids

Open reading frames

The question on the page originate from the summary of the following study material:

Brock Biology of Microorganisms, Global Edition | 9781292235103 | Michael T Madigan, et al

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Molecular Information Flow and Protein Processing - Transcription in Bacteria

14 important questions on Molecular Information Flow and Protein Processing - Transcription in Bacteria

What enzyme catalyzes transcription and forms phosphodiester bonds between the ribonucleotides?

Driven by energy released from the hydrolysis of two energy-rich phosphate bonds of the incoming ribonucleoside triphosphates.

How is the mechanism of RNA synthesis similar to that of DNA synthesis?

Transcription continues until specific sequences called _________ ___________are reached, but unlike DNA replication, which copies the entiregenome, transcription occurs on much smaller units of DNA, oftenas little as a single gene.

Five subunits of RNA polymerase and form the RNAP core enzyme responsible for RNA synthesis using DNA as template and ribonucleotide (rNTP) as substrate.

The core enzyme alone synthesizes RNA, and sigma functions only to recognize the appropriate site on the DNA for transcription to begin (sigma dissociates from the holoenzyme oncea short sequence of RNA has been formed). Once sigma dissociates, _____ is formed.

Why does transcription occur in opposite directions on the two different strands of DNA?

2 highly conserved regions in the promoter that are upstream of (prior to) the transcription start site

Promoters that conform most closely to the consensus sequence and are effective in binding RNA polymerase.

Why is the presence or absence of a specific sigma factor is a mechanism forregulating gene expression?

Segments of DNA that are transcribed into a single RNA molecule bounded by their initiation and termination sites

Three size classes of prokaryotic rRNA:

RNA polymerase proceeds through the operon and transcribes the entire set of genes into a single mRNA called _____. It contains multiple open reading frames.

Portions of the mRNA that actually encode amino acids

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Transcription continues until specific sequences called _ ___are reached, but unlike DNA replication, which copies the entire
genome, transcription occurs on much smaller units of DNA, often
as little as a single gene.

The core enzyme alone synthesizes RNA, and sigma functions only to recognize the appropriate site on the DNA for transcription to begin (sigma dissociates from the holoenzyme once

a short sequence of RNA has been formed). Once sigma dissociates, _____ is formed.

Why is the presence or absence of a specific sigma factor is a mechanism for
regulating gene expression?