How do promoters differ in efficiency? How is the expression of the lac operon i

Question

How do promoters differ in efficiency?

How is the expression of the lac operon inhibited by the lac repressor?

Which two characteristics differentiate promoters from enhancers?

Name the 3 different eukaryotic RNA polymerases and describe the specific genes they transcribe.

What role do small nucleolar ribonucleoproteins (snoRNPs) play in RNA processing?

What is the amino acid error rate in protein synthesis? Is this rate logical in evolutionary terms of function?

What is the first step in the elongation cycle?

Translation can be considered to have three phases or steps: initiation, protein synthesis, and termination. Please compare/contrast the three steps for prokaryotic and eukaryotic translation in each phase.

Explanation / Answer

Answering first four questions according to the answering guidelines of a multi sub-part question.

Q1. The promoters differ in efficiency by virtue of their sequence. A diference in sequence determines the efficiency of RNA polymerase binding to the promoter which is a measure of the efficiency. For e.g. CAAT box in eukaryotes plays an important role in promoter efficiency.

Q2. The lac repressor forms a tetramer and binds tightly to the lac operator site. This binding prevents the transcription of the structural genes involved in lactose metabolism.

Q3. Usually RNA polymerase or transcription factors binds to the promoters whereas activators bind to enhancers. Promoters are present usually about 200bp upstream from the transcription start site whereas enhancers may be located several thousand kilobases apart from the transcription start site.

Q4. The three different eukaryotic RNA polymerases are: a) RNA Pol I - Transcribes rRNA b) RNA Pol II - Transcribes mRNA c) RNA Pol III - Transcribes tRNA.

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.