Transcription & Gene Regulation

What is transcription?

1. RNA polymerase synthesizes an mRNA of the instruction stored as DNA using NTPs

2. one DNA strand is the template strand and the other is non template strand (coding)

3. RNA bases match to template strand and synthesized in 5’ → 3’ direction (U instead of T)

What is the overall function of transcription?

Transcribes DNA into a message

What is the function of RNA Polymerase?

Connects a RNA base to the DNA strand to transcribe the sequence (ex:  AUG → UAC)

Since proteins do jobs, what does this allow?

Cells to function and life to exist

What are proteins based on?

Their shape which is determined by their sequence, and the sequence is determined by the mRNA

True or False: a proteins shape will recognize specific regions and bind to them 

True

What is a promoter?

The region where DNA signals the protein enzyme that builds the RNA Strand and RNA polymerase to start transcription

What binds first to the promoter?

Sigma (protein)

____ is a transcription factor shaped to recognize specific sequence of DNA bases

Sigma

What is the region of DNA that signals RNA polymerase to stop transcription.

The terminator

Describe the steps of transcription.

1. Sigma binds → 2. RNA Polymerase binds to sigma → 3. Changes shape & DNA is opened up → 4. Nucleotides bind

What happens to eukaryotic DNA in transcription?

Condenses due to methyl groups on Cs next to the Gs, then remodeled by chromatin prior to transcription

Can the RNA polymerase bind by itself?

No, it requires assistance from transcription factors (proteins) that are already binded

What is alternative splicing?

RNA can be spliced → spliceosome proteins remove introns and splice together exons

• results in diff proteins that code for single gene (only in eukaryotes)

What are introns?

noncoding regions within a gene that get removed

What are exons?

Protein coding regions

Once splicing is complete in eukaryotes, what does this mean? 

A single DNA sequence can code for multiple proteins

In eukaryotic RNA, what is added to mRNAs?

5’ cap and poly(A) tail to prevent mRNA degradation in the cytoplasm

What prevents mRNA degradation in the cytoplasm?

Poly(A) tail

Describe gene regulation in bacteria?

Controls transcription by receptors (negative) and activators (postive)

What is Positive and Negative Control for gene regulation in bacteria?

• Positive Control: repressor protein shuts down transcription

• Negative Control: activator protein triggers transcription

Describe gene regulation in eukaryotes?

More complex transcription control, has multiple enhancers that increase levels of transcription