Question

You decide to make a construct that places the DNA between the genes upstream to a reporter gene (GFP) in place of Gene 1. The full-length construct has the correct expression pattern in antennal discs. You then create several constructs that delete sections of the upstream DNA and score them for expression. The seven constructs are shown below; the black bars indicate the region(s) deleted in each construct. The data table on the right shows the expression results for each construct.

GFP GFP in leg discs GFP in GFP in antennal wing discs discs absent absent present present absent absent present absent absent present absent absent present absent absent Construct 1 Construct2 Construct 3 Construct 4 Construct 5 Construct 6 Construct 7 absent present absent absent present absent

From these results, you hypothesize that the sequence you have examined contains a promoter for gene 1 (P₁), an enhancer that controls antennal expression (E_A), an enhancer that controls leg and wing expression (E_WL), and an insulator region (I).

Using the data, identify the function of each DNA segment by dragging the labels to their correct locations. Labels can be used once, more than once, or not at all. The labels are Ea, P1, I, and Ewl. They go under the a, b, c, d spots

Answer 1

Arrangement of each region in DNA sequence is as follows:

으으으 GFP P1 EA EwL (Direction of transcription)

Promoter: Starting site for transcription

Enhancer: Increases rate of transcription

Insulator: Blocks a gene being transcribed non-specifically by another enhancer. If it is placed between promoter and enhancer, it blocks the interaction between them, thereby reducing the expression. It has more direct effect on enhancer, if it is directly upstream to the insulator.

Explanation for each construct expression:

Construct 1: It lacks promoter region, hence no expression in all three regions.

Construct 2: It lacks Enhancer for antennal expression (EA), so no expression in antennal discs. But, presence of Insulator after enhancer for leg and wing expression (EWL) region blocks its activity. Hence, no expression in all three regions.

Construct 3: It lacks insulator region. So, expression can be seen in all three regions.

Construct 4: It lacks EWL region, so no expression in wings and legs.

Construct 5: It lacks EWL region and promoter, so no expression in all three regions.

Construct 6: It lacks Insulator and EA region. So, expression can be seen in wings and legs but not in Antennal discs.

Contruct 7: It lacks EWL region and Insulator region. So, Expression can be seen in Antennal discs but not in wings and legs.