Strong and weak promoters are only different in their base sequence. For example
ID: 302599 • Letter: S
Question
Strong and weak promoters are only different in their base sequence. For example, the genes shown below are genetically identical except for their promoter sequences Amount of transcript Promoter sequence (-10 box) 5% TATGAT 75% TATAAT 2. Explain how a single base change in the promoter sequence could have such an effect on promoter strength? In addition to promoter strength, transcription factors also influence transcript produc- tion. Transcription factors are tertiary structure proteins that bind to a specific site on the DNA. Transcription factors have many names, but they will act as either a repressor or an activator. 3. Below are two different transcription factors binding to the promoter region of the same gene. Given theireffect on transcript production, label them as either a repressor or activator. Activator or Repressor? Amount of transcript (compared to maximum) RNA 0.7% Promoter region RNA 100% Promoter region 98Explanation / Answer
Answer 2: TATAAT box is present in the promoter sequence/region of prokaryotic gene. During transcription initiation process, sigma factor (Protein) binds with the promoter region sequences to recruit RNA polymerase. Sigma factor strongly binds with specific sequences at -10 region of the gene. Now, if a single base pair changes in that promoter sequence, sigma factor fails to bind tightly with the promoter sequences. As a result, the efficiency of the transcription reduces and ultimately the transcript production becomes low.
Answer:3 The figure shows (1st one) unavailibility of the binding sequences for RNA Polymerase leading to leaky expression of the gene. The transcription factor binds in the promoter region and prohibits the binding of RNA polymerase. Here, the transcript amount is very low , i.e, 0.7%(minimal transcription). This indicates the transcription factor is a repressor.
Where as, in 2nd image, RNA polymerase tightly binds with promoter region and the transcript production is very high , i.e , 100%. This indicates the transcription factor is an activator.