Chapter 28, Problem 7P

(a)

Summary Introduction

To describe: The effect of increasing the distance between the leader peptide gene and sequence 2 on transcription of the E.coli trp operon.

Introduction:

Transcription attenuation is a mechanism which regulates the translation of a leader peptide by controlling the transcription of structural gene. Trp operon contains two trp codons at attenuator region that forms stem-loop structure. Sequence 1 encodes the leader peptide and sequence 2 is responsible for the constitutive expression.

(b)

Summary Introduction

To describe: The effect of increasing the distance between sequence 2 and sequence3 on transcription of the E.coli trp operon.

Introduction:

In the presence of tryptophan, occurrence of translation of leader sequences result in blocking the sequence 2. Blocking of sequence 2 followed by transcription of sequence 3 and sequence 4, and formation of attenuator structure.

(c)

Summary Introduction

To describe: The affect of removing sequence 4 on transcription of the E.colitrp operon.

Introduction:

In the presence of tryptophan, occurrence of translation of leader sequences result in blocking the sequence 2. Blocking of sequence 2 followed by transcription of sequence 3 and sequence 4, and formation of attenuator structure.

(d)

Summary Introduction

To describe: The effect of changing the two tryptophan (Trp) codons in the leader peptide gene to histidine (His) codons, on transcription of the E.coli trp operon.

Introduction:

Repressible operon represses the expression of structural gene. For example trp-operon have structural gene E, D, C, B and A that are repressed or inactive in the present of tryptophan. As the trp codon forms attenuation structure and make the operon sensitive against the tryptophan.

(e)

Summary Introduction

To describe: The effect of eliminating the ribosome-binding site for the gene that encodes the leader peptide on transcription of the E.coli trp operon.

Introduction:

Transcription attenuation is a mechanism which regulates the translation of a leader peptide by controlling the transcription of structural gene. Trp operon contains two trp codons at attenuator region that forms stem-loop structure. Sequence 1 encodes the leader peptide and sequence 2 is responsible for the constitutive expression

(f)

Summary Introduction

To describe: The effect of changing several nucleotides in sequence 3 so that it can base pair with sequence 4 but not with sequence 2, on transcription of the E.coli trp operon.

Introduction:

Transcription attenuation is a mechanism which regulates the translation of a leader peptide by controlling the transcription of structural gene. Trp operon contains two trp codons at attenuator region that forms stem-loop structure. Sequence 1 encodes the leader peptide and sequence 2 is responsible for the constitutive expression and sequence 3 and sequence 4 is responsible for the formation of attenuation structure.