Gene Regulation

What are the qualities of gene expression on Prokaryotes?

• Gene expression through Transcription and Translation (in cytoplasm)

  • No introns

  • Occur at the same time

  • Regulation occurs during transcription only

What are the qualities of gene expression on Eukaryotes?

• Gene expression is complex

• Gene expression through Transcription, RNA processing, and Translation

  • Regulation occurs during any/all of these steps

Define Operons?

Multiple structural genes controlled together by a single promoter

What are the common operon features?

• Promoter region - binding side of RNA polymerase

• Operator region - binding site of transcription factors

• Structural genes - code being transcribed and translated into products for the cell

What binds to the operate and why?

The Repressor proteins to prevent transcription

What is the role for the Regulatory genes?

To code for transcription factors

What is the point of the Promoter?

To act as a binding site of RNA polymerase

What is the point of the Operator?

To act as a binding site of transcription factors

What is the point of the Operons?

So multiple structural genes can be controlled by a single promoter

What is the point of the Structural Genes?

So genes can be transcribed and translated into products for the cell

What is a trp operon?

An amino acid used to build proteins

There are 2 ways to prevent the synthesis of trp when levels are high

Repression & Attenuation

What does Repression do?

Blocks the initiation of transcription when trp is high

What will happen if No trp is present?

The trp needs to be made and to do so the trp repressor would be unable to bind and stop transcription

What will happen if Trp is present?

Then trp will acts as corepressors blocking RNA polymerase & transcription

What does Attenuation do?

A secondary control mechanism preventing completion of transcription when trp levels are high

What will happen if trp is present in Attenuation?

• The would ribosome pauses at the stop codon

• Which would partially overlap both regions 1 & 2, preventing them from binding

• RNA polymerase continues past region 4 to attenuator

• Region 4 becomes attracted to region 3, pulling together to form a loop

• Weak H bonds between Uracil + Adenine will pull the mRNA away from the template strand

• RNA polymerase falls off

• transcription would stop