BIOL 300 Discussion 9: Transcription

What is the different between Replication and Transcription?

Replication is DNA to DNA

Transcription is from DNA to RNA

What is the Major Enzyme for Replication?

DNA Polymerase

What is the Major Enzyme for Transcription?

RNA Polymerase

What region does Replication occur?

In the Replicon

What region does Transcription occur? In either

Pro: Cytoplasm

Euk: Nucleolus

Nucleoplasm

What are the three steps for Prokaryotic Transcription?

1. Initiation

2. Elongation

3. Termination

What is RNA Polymerase?

It is the enzyme responsible for transcription initiation; synthesizes RNA from DNA

What is Prokaryotic RNA Polymerase composed of?

A core enzyme, a2BB'w(sig)

What is the Holoenzyme of RNA Polymerase composed of?

5 different subunits consisting of 2 alpha, 1 beta, 1 beta prime, and 1 sigma

What is the Prokaryotic Promoter? what binds to it?

A specific DNA sequence where RNA pol binds to begin transcription.

Where are Consensus Sequences located? Why are they important?

Within the Promoters, RNA Pol recognizes these sequences and binds.

What are Consensus Sequences?

Calculated order of most frequent/common residues found at each position in the sequence alignment.

What are Conserved Sequences

Similar or identical sequences in DNA; occur across species

Increasing or Decreasing # of nucleotides between the 2 consensus sequences does what?

Affects transcription rate

Changing nucleotides (insertions/deletions) between the 2 consensus sequences does what?

Does not affect transcription rate.

How many classes of RNA Polymerases are present?

There are three, RNA Pol 1,2, and 3

What is the function of RNA Pol 1?

Synthesizes rRNA

What is the function of RNA Pol 2?

Synthesizes mRNA

What is the function of RNA Pol 3?

synthesizes multiple types of RNA

What are Cis-Acting elements?

Elements located within the DNA sequences

What are Trans-acting elements

Elements that will bind to the Cis-Acting elements (transcription factors)

Which RNA Polymerase has a C-Terminal Domain?

RNA Polymerase 2

What are Enhancers?

DNA sequences that can increase transcription rates by increasing the efficiency by which RNA polymerase binds to a promoter.

Where are promoters located in Eukaryotes? In Prokaryotes?

Around start point in Eukaryotes, Before the start point in Prokaryotes

What is the name of the TAATAT consensus sequence in Eukaryotes? In Prokaryotes?

TATA box in Eukaryotes, Pribnow box in Prokaryotes

What enzyme binds to the promoter in Eukaryotes? In Prokaryotes?

Transcription Factors in Euk.

RNA Polymerase in Prok.

Where is the Pribnow box found? TATA Box? (sequence number)

Pribnow box is -10

TATA box is -25

What proteins are needed for Prokaryotic Transcription initiation? Eukaryotic initiation?

Prokaryotes use Sigma factors,

Eukaryotes use General Transcription Factors

Does RNA polymerase bind directly to the promoter in Prokaryotes?

What about Eukaryotes?

Yes in Prokaryotes,

No in Eukaryotes