Question

The Drosophila regulatory segment that defines the location of Eve stripe 2 contains binding sites for four different transcription regulators: two repressors (Giant and Krüppel) and two activators (Bicoid and Hunchback). For Eve to be efficiently expressed in stripe 2, both repressors must be absent and both activators present. What would you expect to see in flies that lack the gene that encodes Bicoid? (Assume that Bicoid does not influence the expression of Hunchback, Giant, or Krüppel.) Giant Krüppel stripe 2 regulatory DNA segment Bicoid Hunchback Choose one: O A. All 7 stripes would disappear. B. Stripe 2 would expand toward the head of the embryo. C. Stripe 2 would expand toward the tail of the embryo. D. Stripe 2 would become fainter. E. Stripe 2 would become narrower.

Answer 1

Answer: Stripe 2 would become more faint.

Explanation:

Even-skipped (Eve) gene expression is under the control of regulators and activators.

Bicoid and hutchback are activators, the Eve gene under the reporter control present in the region where concentrations of inhibitors are absent.

Stripe 2 would become more faint and would remain at its normal position.

Transcription regulators influence the activity of number of genes but each gene is expressed in right time and in right amount.

The fate of a cell whether become head or tail depends on normal development.

In lack the gene that encodes Bicoid but Bicoid does not influence the expression of Hunchback, Giant, or Krüppel. Therefore, in its absence expression of other genes is not affected but RNA polymerase that is required for transcription will not tightly bind to promoter and therefore protein made is fainter.