Question

Transcription factors that bind to DNA and stimulate transcription are a. repressors. b. small effector molecules. c. activators. d. promoters. e. operators.

Short answer

The transcription factors that bind to DNA and stimulate transcription are c. activators.

Step-by-step solution

Elimination Step

Start by eliminating the terms that do not fulfill the role of binding to DNA and stimulating transcription. In this case, repressors are involved in stopping or slowing down transcription, not stimulating it. Therefore, option a is incorrect. Small effector molecules, option b, are not directly related to the process of transcription. They can influence it, but they do not bind to the DNA. Promoters (option d) are DNA sequences where RNA polymerase and transcription factors bind to initiate transcription, but they are not the transcription factors that stimulate transcription. Operators (option e) are DNA sequences in the operon to which repressors bind, not the transcription factors that stimulate transcription.

Selection Step

The only option left is 'c. activators'. Activators are indeed transcription factors that bind to DNA and stimulate transcription, fitting the description given in the exercise.

Key concepts

Gene Expression Regulation

Understanding how genes are turned on and off is essential to comprehending the biological processes that keep living organisms functioning. Gene expression regulation is a complex mechanism that ensures genes are expressed at the right time, place, and in the correct amounts. This regulation can occur at various stages, including transcription, RNA processing, RNA transport, translation, and even after proteins have been created.

At the transcriptional level, a pivotal control point, sequences in the DNA called promoters provide binding sites for RNA polymerase and transcription factors. These elements work collaboratively to catalyze the synthesis of RNA from DNA. However, promoters alone aren't enough to accelerate transcription — here is where regulatory elements such as enhancers and silencers come into play. They can exponentially increase or decrease the likelihood of transcription occurring by interacting with specific transcription factors.

Activators in Transcription

In the magnificent play of gene expression, activators are the directors that signal the 'action!' cue. They are a subgroup of transcription factors that bind to specific DNA sequences, often located in the enhancer regions, to boost the rate of transcription.

An activator’s main role is to facilitate the assembly of the transcription machinery at the promoter. This is achieved by helping to recruit RNA polymerase to the site of transcription, or by altering the chromatin structure to make the DNA more accessible. In the context of our exercise, when students are asked about transcription factors that bind to DNA and stimulate transcription, understanding activators and how they propel the transcriptional machinery into action is crucial to grasping the underlying principles of gene regulation.

Transcriptional Activation

Transcriptional activation is the splash of the start gun that sets the transcription machinery in motion. This process is where all the preparatory mechanisms of gene expression coalesce to initiate the synthesis of mRNA from a DNA template.

A carefully coordinated series of interactions between activators, coactivators, and other transcription factors leads to the recruitment of RNA polymerase II and the initiation complex to the promoter region. These interactions can also involve modifications to the histones and chromatin remodelling, making the DNA more accessible. By elaborating on transcriptional activation, we empower students to visualize the ‘behind-the-scenes’ orchestration that dictates when and how a gene is expressed, rounding out their comprehension of the exercise at hand.