Question

(a) Did deletion of any of the possible control elements cause a reduction in reporter gene expression? If so, which one (s), and how can you tell? (b) If loss of a control element causes a reduction in gene expression, what must be the normal role of that control element? Provide a biological explanation for how the loss of such a control element could lead to a reduction in gene expression.

Short answer

(a) Yes, the deletion of the possible control element 3 caused a reduction in reporter gene expression because the construct produced less than 50% of the relative level of reporter mRNA than the control group.

(b) The role of element 3 must be to activate gene expression.

In the absence of the control element, the activators do not bind to the enhancer. As a result, the expression of genes decreases.

Step-by-step solution

Explanation for part ‘a’

When the level of reporter mRNA produced from all the constructs was compared, it was observed the DNA construct with deleted possible control element 3 synthesized the least amount of mRNA.

It produced less than 50% of the reporter mRNA than the control level. This exhibits that the deletion of control element 3 significantly impacted the gene expression as very little reporter mRNA is produced from this construct.

Explanation for part ‘b’

The deletion of control element 3 reduces the expression of the gene. This means the role of the control element is to activate the expression of genes. This is because the control elements such as promoter or enhancer region are involved in regulating gene expression.

Effect of deleted control element on gene expression

Activators are DNA-binding protein that binds to the enhancer region of the DNA and promotes gene expression. In the experiment, the activators cannot bind to the enhancer region in the absence of control element 3 to activate gene expression.

As a result, there is a reduction in gene expression level in the absence of the control element.